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coatings
Article
Effect of Annealing on the Characteristics of CoFeBY
Thin Films
Wen-Jen Liu 1, Yung-Huang Chang 2, Yuan-Tsung Chen 3,* , Yi-Chen Chiang 3, Ding-Yang Tsai 3, Te-Ho Wu 3and
Po-Wei Chi 4
Citation: Liu, W.-J.; Chang, Y.-H.;
Chen, Y.-T.; Chiang, Y.-C.; Tsai, D.-Y.;
Wu, T.-H.; Chi, P.-W. Effect of
Annealing on the Characteristics of
CoFeBY Thin Films. Coatings 2021,11,
250. https://doi.org/10.3390/
coatings11020250
Academic Editor: Alberto Palmero
Received: 20 January 2021
Accepted: 10 February 2021
Published: 20 February 2021
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1Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan;
jurgen@isu.edu.tw
2Bachelor Program in Industrial Technology, National Yunlin University of Science and Technology,
123 University Road, Section 3, Douliou, Yunlin 64002, Taiwan; g9213752@gmail.com
3
Graduate School of Materials Science, National Yunlin University of Science and Technology, 123 University
Road, Section 3, Douliou, Yunlin 64002, Taiwan; M10947001@yuntech.edu.tw (Y.-C.C.);
M10847010@yuntech.edu.tw (D.-Y.T.); wuth@yuntech.edu.tw (T.-H.W.)
4Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan; jacky01234567891@hotmail.com
*Correspondence: ytchen@yuntech.edu.tw; Tel.: +886-5-534-2601
Abstract:
In this study, the addition of Y to CoFeB alloy can refine the grain size to study the magnetic,
adhesion and optical properties of as-deposited and annealed CoFeB alloy. XRD analysis shows that
CoFeB(110) has a BCC CoFeB (110) nanocrystalline structure with a thickness of 10–50 nm under
four heat-treatment conditions, and a CoFeB(110) peak at 44◦(2θ). The measurements of saturation
magnetization (M
S
) and low frequency alternate-current magnetic susceptibility (
χac
) revealed a
thickness effect owed to exchange coupling. The maximum M
S
of the 300
◦
C annealed CoFeBY film
with a thickness of 50 nm was 925 emu/cm
3
(9.25
×
10
5
A/m). The maximum
χac
value of the 300
◦
C
annealed CoFeBY nanofilms with a thickness of 50 nm was 0.165 at 50 Hz. After annealing at 300
◦
C,
CoFeBY nanofilms exhibited the highest surface energy of 31.07 mJ/mm
2
, where the thickness of the
nanofilms was 40 nm. Compared with the as-deposited CoFeBY nanofilms, due to the smaller average
grain size after annealing, the transmittance of the annealed nanofilms increased. Importantly, when
a CoFeB seed or buffer layer was replaced by a CoFeBY nanofilm, the thermal stability of the CoFeBY
nanofilms was improved, promoting themselves on the practical MTJ applications.
Keywords:
annealed Co
40
Fe
40
B
10
Y
10
nanofilms; low-frequency alternating current magnetic suscep-
tibility (χac); optimal resonance frequency (fres); surface energy; adhesion; transmittance
1. Introduction
Since the discovery of Co
50
Fe
50
in CoFe systems by Ellis in 1927 and Elmen in 1929, it
has shown good soft magnetic properties [
1
]. These characteristics include high saturation
magnetization (M
S
) and high Curie temperature (T
C
). Due to its excellent performance,
Co–Fe system has attracted extensive attention. According to the above characteristics,
Co-Fe alloys have the advantages of low coercivity (Hc) and good mechanical properties.
However, with increasing annealing temperature, CoFe alloy has the disadvantage of
serious degradation of magnetic anisotropy, which makes the effective use of these magnetic
devices at high temperature difficult. Adding a third element to the CoFe matrix can
help to overcome this problem [
2
–
7
]. Therefore, to find a kind of component that can
improve the magnetothermal stability has become a primary research goal. For example,
CoFeB thin films are widely used as free or pinned layers of spin valued magnetic tunnel
junctions (MTJ) due to their high spin polarization and high tunneling magnetoresistance
(TMR). They can be used in magnetoresistance random access memory (MRAM) and
recording head devices [
8
–
13
]. Recently, more and more scholars have become interested in
high-abundance rare earth magnetic materials. Due to the unique properties of rare earth
Coatings 2021,11, 250. https://doi.org/10.3390/coatings11020250 https://www.mdpi.com/journal/coatings
Coatings 2021,11, 250 2 of 14
elements, the high temperature resistance, mechanical strength, ductility and other physical
properties of magnetic films can be improved. However, they can form compounds with
transition metals such as iron, nickel and cobalt, some of which have Curie temperatures
much higher than room temperature. Perhaps its properties can be used to improve the
thermal stability of magnetic films at high temperature. Researchers who study magnetism
and microstructure add yttrium (Y) to magnetic materials, or use Y to replace other elements
in magnetic materials. Y addition plays the important role, including substitution or
institute site in the material. When the radius of the Y atom is slightly larger, Y atoms can
increase the degree of mismatch between atoms and promote the formation of amorphous
phase. Y has a unique external electronic structure, which can remove impurities, prevent
segregation and refine grains. Fe-Y composite oxides have a special place in temperature
ferromagnetism [
14
]. In addition, the addition of a small amount of Y can significantly
improve the corrosion resistance and chemical stability of the passive film [
15
,
16
]. A prior
investigation was focused on the transition from amorphous state to nanocrystalline state
and/or the improvement of nanocrystalline state to change the specific properties and
magnetic properties of the films [
17
]. For example, substituting 2 at% Y for Nb can slow
down the diffusion rate of alloying elements in fenbb alloy and reduce the growth of
grains [
18
]. Compared with other rare earth elements such as Gd, TB or Dy, Y can obtain
higher permeability [
19
]. When Y was doped into Finemet to investigate its effect on
magnetic properties, Y was able to replace Nb to refine the grain [
20
]. In terms of hard
magnetism, Fan et al. pointed out that the Y element can replace Ce in permanent magnet
materials, which improves the thermal stability of magnetism and reduces the remanence
coefficient and coercivity [
21
]. Zhang et al. stated that the addition of Y to NdFeB could
significantly reduce the coercivity and effectively improve its heat resistance [
22
]. In the
fields of soft magnetism, some scholars have successfully developed bulk-sized ternary
Fe-X-B (X = Sc, Y, Dy, Ho, Er) amorphous alloys with the minor addition of rare earth
elements. In addition, Fe-Y-B has high potential for industrial applications due to its low
cost [
23
,
24
]. To date, several studies have shown that adding Y or increasing Y content can
not only reduce the coercivity of the alloy, but also improve the thermal stability and reduce
the production cost. However, there are few studies on the addition of rare earth elements
in soft magnetic CoFe alloys. Based on the above literature, CoFeB thin films are commonly
used in MTJ applications, but the processing temperature is high, so it is necessary to
improve the thermal stability. To improve the magneto-thermal stability of CoFeB alloy, it
is very important to study the effect of Y addition on the structure and magnetic properties
of CoFeB alloy. The purpose of this study is to investigate the changes of the structure
and magnetic properties of CoFeBY films with the thickness of the films, and to study the
CoFeBY films after heat treatment, so as to determine whether they will change due to
the high temperature environment, thus changing their magnetic efficiency. When the
annealing temperature is 250
◦
C, the CoFeB layer is amorphous, but when the annealing
temperature is increased to 300
◦
C, the amorphous phase becomes nanocrystalline, which
leads to the TMR change of MTJ [
25
]. In this study, CoFeBY nanofilms were sputtered
at room temperature (RT). Then the annealing temperature is set between 100
◦
C and
300
◦
C to determine whether the addition of Y can improve the thermal stability of the
magnetic film at higher temperatures. However, few studies have been carried out on their
magnetic-optical properties; therefore, this study discusses the transmittance of CoFeBY
thin films. The main purpose of this study is to investigate the structure and magnetic
properties of CoFeBY thin films with different thicknesses, and to discuss the structure,
magnetic properties, adhesion and optical properties of CoFeBY films after heat treatment.
2. Materials and Methods
CoFeBY nanofilms with a thickness (t
f
) of 10–50 nm were sputtered on glass substrate
at RT by direct current (DC) magnetron sputtering with 50 W power. After that, the progress
followed by four conditions: (a) the as-deposited films were kept at RT, (b) annealed at
a treatment temperature (T
A
) at 100
◦
C for 1 h, (c) annealed at 200
◦
C for 1 h, and (d)
Coatings 2021,11, 250 3 of 14
annealed at 300
◦
C for 1 h. The power density iwass 1.65 W/cm
2
and the deposition rate
was 1.2 nm/min. The base pressure of the chamber was 3
×
10
−7
Torr, and the working
pressure of Ar was 3
×
10
−3
Torr. The pressure in the ex-situ annealed condition was
2.5 ×10−3
Torr with a specific Ar gas. The alloy target for the composition of CoFeBY was
40 at% Co, 40 at% Fe, 10 at% B and 10 at% Y. The surface morphology was detected by
field emission scanning electron microscopy (SEM, Hitachi SU 8200, Tokyo, Japan). The
grazing incidence X-ray Diffraction (GIXRD) patterns of CuK
α
1 (PAN analytical X’pert
PRO MRD, Malvern Panalytical Ltd., Cambridge, UK) and low angle diffraction incidence
of about two-degree angle were used to determine the structure of CoFeBY films. The in-
plane low-frequency alternate-current magnetic susceptibility (
χac
) and hysteresis loops of
Co
40
Fe
40
B
10
Y
10
were studied by
χac
analyzer (XacQuan, MagQu Co. Ltd., New Tapei City,
Taiwan) and alternating gradient magnetometer (AGM, PMC, OH, USA). Firstly, the
standard sample was calibrated by external magnetic field
χac
analyzer. Then, the sample
was inserted into the
χac
analyzer. The driving frequency is between 10 and 25,000 Hz.
χac
was determined by magnetization. All samples had the same shape and size to eliminate
demagnetization. The
χac
valve is an arbitrary unit (a.u.), because the alternating current
result corresponds to the reference standard sample, which is a comparative value. The
relationship between magnetic susceptibility and frequency was measured by means of
χac
analyzer. The optimal resonance frequency (f
res
) was measured by the
χac
analyzer,
which represents the frequency of the maximum
χac
. Before measurement, the contact
angle should be properly air-cleaned on the surface. The contact angles of CoFeBY film
were measured with deionized (DI) water and glycerol. The contact angles were measured
when the samples take out from the chamber. The surface energy is obtained from the
contact angles and some calculations [
26
–
28
]. The transmittance of CoFeBY was measured
by spectral intelligent analyzer. The wavelength of visible light was from 500 nm to 800 nm.
3. Results
3.1. Structure Property
Figure 1displays the XRD patterns of Co
40
Fe
40
B
10
Y
10
nanofilms with a thickness of
10 to 50 nm on glass substrates under four conditions. Figure 1a shows the XRD patterns
for the nanofilms at RT, while those of samples annealed at 100, 200 and 300
◦
C are shown
in Figure 1b,c, respectively. The results of XRD are shown at different diffracted angles
(2
θ
) between 35 and 60 degrees. The (110) body-centered cubic (BCC) structure for the
CoFeB nanofilms was revealed to be around 2
θ
= 44
◦
, indicating that the CoFeBY nanofilms
belonged to a crystallized state [
29
]. Moreover, the YFeO
3
oxide peaks found at 2
θ
= 37.3
◦
may be attributed to the Y doping [30].
Coatings 2021,11, 250 4 of 14
Coatings 2021, 10, x FOR PEER REVIEW 4 of 14
Figure 1. XRD patterns of CoFeBY films. (a) RT, (b) after annealing at 100 °C, (c) after annealing at 200 °C, (d) after an-
nealing at 300 °C.
Figure 2a shows the full width at half maximum (FWHM, B) of the CoFeB (110) peak
obtained in four conditions. The average crystallite sizes could be calculated according to
the FWHM parameters obtained from the XRD patterns. Using the Scherrer formula (1),
the average grain size of CoFeBY films under the studied conditions was calculated with
CoFeB (110) peak.
Scherrer formula is [31]:
D = kλ/Bcosθ (1)
where k (0.89) is the Scherrer’s constant, λ is the X-ray wavelength of Cu Kα1 line, B is the
FWHM of the CoFeB (110) diffraction peaks, and θ is the half-angle of the diffraction
peak. Figure 2b shows the average grain sizes, which were estimated from the half
maximum (FWHM, B) of the CoFeB (110) peak under four conditions. The results
demonstrated that the grain sizes of the films were related to the thickness, and the
crystallinity of the films increased with the increase of thickness. The grain sizes of
CoFeBY after annealing were smaller than those at RT, because the grain can be refined
by adding an appropriate amount of Y [22].
Figure 1.
XRD patterns of CoFeBY films. (
a
) RT, (
b
) after annealing at 100
◦
C, (
c
) after annealing at 200
◦
C, (
d
) after annealing
at 300 ◦C.
Figure 2a shows the full width at half maximum (FWHM, B) of the CoFeB (110) peak
obtained in four conditions. The average crystallite sizes could be calculated according to
the FWHM parameters obtained from the XRD patterns. Using the Scherrer formula (1),
the average grain size of CoFeBY films under the studied conditions was calculated with
CoFeB (110) peak.
Scherrer formula is [31]:
D=kλ/Bcosθ(1)
where k (0.89) is the Scherrer’s constant,
λ
is the X-ray wavelength of Cu K
α
1 line, B is the
FWHM of the CoFeB (110) diffraction peaks, and
θ
is the half-angle of the diffraction peak.
Figure 2b shows the average grain sizes, which were estimated from the half maximum
(FWHM, B) of the CoFeB (110) peak under four conditions. The results demonstrated that
the grain sizes of the films were related to the thickness, and the crystallinity of the films
increased with the increase of thickness. The grain sizes of CoFeBY after annealing were
smaller than those at RT, because the grain can be refined by adding an appropriate amount
of Y [22].
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(a)
(b)
Figure 2. (a) The full width at half maximum (FWHM, B) of CoFeBY films, (b) the average grain
size of CoFeBY films.
3.2. Magnetic Properties
Figure 3a–d plot the magnetic hysteresis loops of CoFeBY films under four condi-
tions, in which the thicknesses were measured between 10 and 50 nm by AGM meas-
urement, and the magnetic field is parallel to the film surface. The in-plane external field
(Hext) field of 500 Oe (3.98 × 104 A/m) was sufficient to observe the saturated magnetic
spin status. The enlarged image illustrates low coercivity (HC), which suggests that the
CoFeBY films were soft magnetic. These data are summarized in Table 1, which shows
the magnetic properties of the nanofilms that were obtained by AGM. Figure 4 shows the
corresponding saturation magnetization (MS) of the CoFeBY film under four conditions.
The results revealed that the observed MS increased with the increase of thickness, indi-
cating the thickness effect of MS on CoFeBY films. The MS value of CoFeBY films in-
creased with the increase of annealing temperature. However, Ms was the highest after
annealing at 300 °C, which was the best heat-resistant temperature in this study. The re-
sults show that the size of CoFeBY nanofilms is affected by the grain refinement, which
improves the ferromagnetic spin exchange coupling and thus increases the Ms [32]. In
addition, iron oxide was also detected in the XRD results, which may be the characteristic
of antiferromagnetism, so the magnetization of iron oxide was deduced. In this study, the
addition of Y and annealed treatment can increase the magnetization.
The corresponding HC is displayed in Table 1. HC increased from 1.5 Oe to 15.1 Oe
when tf ranged from 10 to 50 nm at room temperature; HC increased from 3.5 Oe to 18.8
Figure 2.
(
a
) The full width at half maximum (FWHM, B) of CoFeBY films, (
b
) the average grain size
of CoFeBY films.
3.2. Magnetic Properties
Figure 3a–d plot the magnetic hysteresis loops of CoFeBY films under four conditions,
in which the thicknesses were measured between 10 and 50 nm by AGM measurement, and
the magnetic field is parallel to the film surface. The in-plane external field (H
ext
) field of
500 Oe (3.98
×
10
4
A/m) was sufficient to observe the saturated magnetic spin status. The
enlarged image illustrates low coercivity (H
C
), which suggests that the CoFeBY films were
soft magnetic. These data are summarized in Table 1, which shows the magnetic properties
of the nanofilms that were obtained by AGM. Figure 4shows the corresponding saturation
magnetization (M
S
) of the CoFeBY film under four conditions. The results revealed that
the observed M
S
increased with the increase of thickness, indicating the thickness effect
of M
S
on CoFeBY films. The M
S
value of CoFeBY films increased with the increase of
annealing temperature. However, Ms was the highest after annealing at 300
◦
C, which
was the best heat-resistant temperature in this study. The results show that the size of
CoFeBY nanofilms is affected by the grain refinement, which improves the ferromagnetic
spin exchange coupling and thus increases the Ms [
32
]. In addition, iron oxide was also
detected in the XRD results, which may be the characteristic of antiferromagnetism, so the
magnetization of iron oxide was deduced. In this study, the addition of Y and annealed
treatment can increase the magnetization. Adding Y and heat treatment can increase the
amount of magnetization.
Coatings 2021,11, 250 6 of 14
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Oe when tf ranged from 10 to 50 nm following annealing at 100 °C; HC increased from 4.5
Oe to 24.8 Oe when tf ranged from 10 to 50 nm following annealing at 200 °C; HC in-
creased from 12.5 Oe to 23.1 Oe when tf ranged from 10 to 50 nm following annealing at
300 °C. In this study, the addition of Y led to the increase of HC, because the addition of Y
refines the grain size, leading to an increase of HC. However, if the HC of CoFeBY films is
between 10 and 20 Oe, and if they have high MS, the CoFeBY films will have soft mag-
netism, thus making them suitable for MRAM and recording head applications. The HC
of nanofilm is usually enhanced by decreasing the grain size, which is an effect related to
the transition from magnetic multi-domains to single domains [33,34].
Figure 3. In-plane magnetic hysteresis loop of CoFeBY nanofilms: (a) RT, (b) after annealing at 100 °C, (c) after annealing
at 200 °C, (d) after annealing at 300 °C.
Table 1. Coercivity (Hc) of CoFeBY nanofilms.
Thickness
(nm)
RT
(Oe)
After
Annealing at
100 °C (Oe)
After
Annealing at
200 °C (Oe)
After
Annealing at
300 °C (Oe)
10 1.5 3.5 4.5 12.5
20 12.3 12.0 15.8 13.4
30 12.0 18.0 12.9 20.3
40 15.1 15.1 24.1 21.9
50 12.5 18.8 24.8 23.1
Figure 3.
In-plane magnetic hysteresis loop of CoFeBY nanofilms: (
a
) RT, (
b
) after annealing at 100
◦
C, (
c
) after annealing at
200 ◦C, (d) after annealing at 300 ◦C.
Table 1. Coercivity (Hc) of CoFeBY nanofilms.
Thickness
(nm)
RT
(Oe)
After Annealing at
100 ◦C (Oe)
After Annealing at
200 ◦C (Oe)
After Annealing at
300 ◦C (Oe)
10 1.5 3.5 4.5 12.5
20
12.3
12.0 15.8 13.4
30
12.0
18.0 12.9 20.3
40
15.1
15.1 24.1 21.9
50
12.5
18.8 24.8 23.1
Coatings 2021, 10, x FOR PEER REVIEW 7 of 14
Figure 4. Saturation magnetization (MS) of CoFeBY nanofilms.
Figure 5a–d show the results of CoFeBY films with thicknesses from 10 to 50 nm at
four conditions (RT, 100, 200 and 300 °C) under which the low-frequency alternat-
ing-current magnetic susceptibility (χac) was studied. The low frequencies were in the
range of 50 to 25,000 Hz. The results showed that the thickness of CoFeBY was between
10 and 50 nm, and the χac values of tf decreased with the increase of frequency (Hz). The
maximum χac corresponding to various CoFeBY thicknesses under four conditions is
shown in Figure 6. It could be found that the maximum χac value was 0.053 when tf was
50 nm at RT; the maximum χac value was 0.074 when tf was 50 nm at 100 °C; the maxi-
mum χac value was 0.152 when tf was 50 nm at 200 °C; and the maximum χac value was
0.165 when tf was 50 nm at 300 °C. Obviously, these results revealed the thickness effect
of χac in CoFeBY films. With the increase of tf, the increase of χac was due to the thickness
effect. The maximum χac value of annealed CoFeBY films was larger than that at RT. This
is because CoFeBY films are affected by grain refinement, which improves the ferro-
magnetic spin exchange coupling and increases the χac value. Table 2 shows the optimal
resonance frequency (ƒres) of CoFeBY. The maximum χac indicated that the spin sensitivity
was the highest at the optimal resonant frequency. The peak of χac reflected the spin ex-
change-coupling interaction and dipole moment of the domain at frequency [35]. Addi-
tionally, the ƒres value of nanofilm is below 500 Hz, which allows CoFeBY nanofilm to be
applied in soft magnetic devices. It was found that the ƒres values of all CoFeBY thick-
nesses were in the range from 50 to 500 Hz, indicating the maximum χac had the strongest
spin sensitivity at this frequency [36].
Figure 4. Saturation magnetization (MS) of CoFeBY nanofilms.
Coatings 2021,11, 250 7 of 14
The corresponding H
C
is displayed in Table 1. H
C
increased from 1.5 Oe to 15.1 Oe
when t
f
ranged from 10 to 50 nm at room temperature; H
C
increased from 3.5 Oe to 18.8 Oe
when t
f
ranged from 10 to 50 nm following annealing at 100
◦
C; H
C
increased from 4.5 Oe
to 24.8 Oe when t
f
ranged from 10 to 50 nm following annealing at 200
◦
C; H
C
increased
from 12.5 Oe to 23.1 Oe when t
f
ranged from 10 to 50 nm following annealing at 300
◦
C. In
this study, the addition of Y led to the increase of H
C
, because the addition of Y refines the
grain size, leading to an increase of H
C
. However, if the H
C
of CoFeBY films is between
10 and 20 Oe, and if they have high M
S
, the CoFeBY films will have soft magnetism, thus
making them suitable for MRAM and recording head applications. The H
C
of nanofilm is
usually enhanced by decreasing the grain size, which is an effect related to the transition
from magnetic multi-domains to single domains [33,34].
Figure 5a–d show the results of CoFeBY films with thicknesses from 10 to 50 nm at four
conditions (RT, 100, 200 and 300
◦
C) under which the low-frequency alternating-current
magnetic susceptibility (
χac
) was studied. The low frequencies were in the range of 50 to
25,000 Hz. The results showed that the thickness of CoFeBY was between 10 and 50 nm,
and the
χac
values of t
f
decreased with the increase of frequency (Hz). The maximum
χac
corresponding to various CoFeBY thicknesses under four conditions is shown in
Figure 6
.
It could be found that the maximum
χac
value was 0.053 when t
f
was 50 nm at RT; the
maximum
χac
value was 0.074 when t
f
was 50 nm at 100
◦
C; the maximum
χac
value was
0.152 when t
f
was 50 nm at 200
◦
C; and the maximum
χac
value was 0.165 when t
f
was 50
nm at 300
◦
C. Obviously, these results revealed the thickness effect of
χac
in CoFeBY films.
With the increase of t
f
, the increase of
χac
was due to the thickness effect. The maximum
χac
value of annealed CoFeBY films was larger than that at RT. This is because CoFeBY
films are affected by grain refinement, which improves the ferromagnetic spin exchange
coupling and increases the
χac
value. Table 2shows the optimal resonance frequency
(
ƒres
) of CoFeBY. The maximum
χac
indicated that the spin sensitivity was the highest
at the optimal resonant frequency. The peak of
χac
reflected the spin exchange-coupling
interaction and dipole moment of the domain at frequency [
35
]. Additionally, the
ƒres
value of nanofilm is below 500 Hz, which allows CoFeBY nanofilm to be applied in soft
magnetic devices. It was found that the
ƒres
values of all CoFeBY thicknesses were in the
range from 50 to 500 Hz, indicating the maximum
χac
had the strongest spin sensitivity at
this frequency [36].
Table 2. Optimal resonance frequency for films of various thicknesses.
Thickness
(nm)
RT
(Hz)
After Annealing at
100 ◦C (Hz)
After Annealing at
200 ◦C (Hz)
After Annealing at
300 ◦C (Hz)
10 50 50 50 50
20 50 50 50 50
30 50 50 50 50
40 50 100 100 50
50 50 50 50 50
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Figure 5. The low-frequency alternate-current magnetic susceptibility (χac) as a function of the frequency from 10 to
25,000 Hz. (a) RT, (b) after annealing at 100 °C, (c) after annealing at 200 °C, (d) after annealing at 300 °C.
Figure 6. Maximum alternate-current magnetic susceptibility for the CoFeBY films.
Table 2. Optimal resonance frequency for films of various thicknesses.
Thickness
(nm)
RT
(Hz)
After Annealing
at 100 °C (Hz)
After Annealing
at 200 °C (Hz)
After Annealing
at 300 °C (Hz)
10 50 50 50 50
20 50 50 50 50
30 50 50 50 50
40 50 100 100 50
50 50 50 50 50
Figure 5.
The low-frequency alternate-current magnetic susceptibility (
χac
) as a function of the frequency from 10 to
25,000 Hz. (a) RT, (b) after annealing at 100 ◦C, (c) after annealing at 200 ◦C, (d) after annealing at 300 ◦C.
Coatings 2021, 10, x FOR PEER REVIEW 8 of 14
Figure 5. The low-frequency alternate-current magnetic susceptibility (χac) as a function of the frequency from 10 to
25,000 Hz. (a) RT, (b) after annealing at 100 °C, (c) after annealing at 200 °C, (d) after annealing at 300 °C.
Figure 6. Maximum alternate-current magnetic susceptibility for the CoFeBY films.
Table 2. Optimal resonance frequency for films of various thicknesses.
Thickness
(nm)
RT
(Hz)
After Annealing
at 100 °C (Hz)
After Annealing
at 200 °C (Hz)
After Annealing
at 300 °C (Hz)
10 50 50 50 50
20 50 50 50 50
30 50 50 50 50
40 50 100 100 50
50 50 50 50 50
Figure 6. Maximum alternate-current magnetic susceptibility for the CoFeBY films.
3.3. Surface Morphology
To study the surface morphology and magnetic results, SEM images of CoFeBY at
40 nm were observed under four conditions, as shown in Figure 7. Figure 7a shows a looser
surface morphology in the as-deposited state. The surface morphology after annealing at
100
◦
C is shown in Figure 7b, which shows the loose surface phenomenon. In Figure 7c,
the surface morphology after annealing at 200
◦
C shows a dense distribution. The surface
morphology of annealed at 300
◦
C was more densely distributed, as shown in Figure 7d.
In addition, the surface morphology w very close to magnetism. In the cases of
Figure 7c,d
,
some defects can be found, which lead to the enhancement of domain wall pinning effect.
Coatings 2021,11, 250 9 of 14
This can induce high coercivity and improve the spin coupling strength [
37
–
40
]. The
susceptibility is also related to magnetic noise and exchange coupling. High susceptibility
can enhance the strong dipole interaction effect [41].
Coatings 2021, 10, x FOR PEER REVIEW 9 of 14
3.3. Surface Morphology
To study the surface morphology and magnetic results, SEM images of CoFeBY at
40 nm were observed under four conditions, as shown in Figure 7. Figure 7a shows a
looser surface morphology in the as-deposited state. The surface morphology after an-
nealing at 100 °C is shown in Figure 7b, which shows the loose surface phenomenon. In
Figure 7c, the surface morphology after annealing at 200 °C shows a dense distribution.
The surface morphology of annealed at 300 °C was more densely distributed, as shown
in Figure 7d. In addition, the surface morphology w very close to magnetism. In the cas-
es of Figure 7c,d, some defects can be found, which lead to the enhancement of
domain
(a) (b)
(c) (d)
Figure 7. SEM micrographs of CoFe40BY 40 nm. (a) RT, (b) after annealing at 100 °C, (c) after an-
nealing at 200 °C, (d) after annealing at 300 °C.
3.4. Analysis of Surface Energy and Adhesion
Table 3 displays the contact angle (θ) of the CoFeBY at RT. The contact angle of the
films was investigated using DI water and glycerol. Table 3 shows the result of the con-
tact angles (θ) of the CoFeBY using DI water, which were 81.7°, 81.1°, 80.9°, 81.3°, and
81.0°, as well as the contact angles (θ) with glycerol, which were 78.4°, 78.2°, 78.8°, 80.8°,
and 79.5°, respectively.
Figure 7.
SEM micrographs of CoFe
40
BY 40 nm. (
a
) RT, (
b
) after annealing at 100
◦
C, (
c
) after
annealing at 200 ◦C, (d) after annealing at 300 ◦C.
3.4. Analysis of Surface Energy and Adhesion
Table 3displays the contact angle (
θ
) of the CoFeBY at RT. The contact angle of the
films was investigated using DI water and glycerol. Table 3shows the result of the contact
angles (
θ
) of the CoFeBY using DI water, which were 81.7
◦
, 81.1
◦
, 80.9
◦
, 81.3
◦
, and 81.0
◦
, as
well as the contact angles (
θ
) with glycerol, which were 78.4
◦
, 78.2
◦
, 78.8
◦
, 80.8
◦
, and 79.5
◦
,
respectively.
Table 3. Average contact angles of CoFeBY nanofilms at RT with DI water and glycerol.
Co40Fe40 B10Y10 (10–50 nm) Contact Angle (θ) with DI
Water as Test Liquid
Contact Angle (θ) with
Glycerol as Test Liquid
10 nm 81.7◦78.4◦
20 nm 81.1◦78.2◦
30 nm 80.9◦78.8◦
40 nm 81.3◦80.8◦
50 nm 81.0◦79.5◦
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Table 4displays the contact angle (
θ
) of the Glass/CoFeBY at 100
◦
C. The contact
angle of the films was investigated using DI water and glycerol. It shows the result of the
contact angles (
θ
) of the CoFeBY using DI water, which were 79.4
◦
, 79.3
◦
, 79.4
◦
, 81.0
◦
, and
80.8
◦
, as well as the contact angles (
θ
) with glycerol, which were 77.8
◦
, 76.9
◦
, 77.6
◦
, 79.7
◦
,
and 80.0◦, respectively.
Table 4.
Average contact angles of CoFeBY nanofilms after annealing at 100
◦
C with DI water and
glycerol.
Co40Fe40 B10Y10 (10–50 nm) Contact Angle (θ) with DI
Water as Test Liquid
Contact Angle (θ) with
Glycerol as Test Liquid
10 nm 79.4◦77.8◦
20 nm 79.3◦76.9◦
30 nm 79.4◦77.6◦
40 nm 81.0◦79.7◦
50 nm 80.8◦80.0◦
Table 5displays the contact angle (
θ
) of the CoFeBY at 200
◦
C. The contact angle of the
films was investigated using DI water and glycerol. Table 5shows the result of the contact
angles (
θ
) of the CoFeBY using DI water, which were 77.6
◦
, 78.3
◦
, 78.0
◦
, 79.5
◦
, and 79.7
◦
, as
well as the contact angles (
θ
) with glycerol, which were 74.0
◦
, 73.2
◦
, 77.2
◦
, 79.2
◦
, and 79.5
◦
,
respectively.
Table 5.
Average contact angles of CoFeBY nanofilms after annealing at 200
◦
C with DI water and
glycerol.
Co40Fe40 B10Y10 (10–50 nm) Contact Angle (θ) with DI
Water as Test Liquid
Contact Angle (θ) with
Glycerol as Test Liquid
10 nm 77.6◦74.0◦
20 nm 78.3◦73.2◦
30 nm 78.0◦77.2◦
40 nm 79.5◦79.2◦
50 nm 79.7◦79.5◦
Table 6shows the annealed 300
◦
C result of the contact angles (
θ
) of the CoFeBY using
DI water, which were 78.1
◦
, 78.0
◦
, 76.8
◦
, 72.9
◦
, and 71.7
◦
, as well as the contact angles (
θ
)
with glycerol, which were 75.9
◦
, 77.0
◦
, 75.8
◦
, 72.7
◦
, and 71.6
◦
, respectively. From the above
results, the contact angles of all CoFeBY films under RT, 100, 200 and 300
◦
C were less
than 90
◦
, indicating that the films were hydrophilic. When films are hydrophilic, they will
have good wetting effect. In addition, the contact angle was closely related to the surface
energy. When the surface free energy is high, the liquid absorption is large and the liquid
absorption area is large, which leads to the decrease of the contact angle
[42]
. The surface
energy was calculated according to the contact angle and Young’s equation [26–28].
Table 6.
Average contact angles of CoFeBY nanofilms after annealing at 300
◦
C with DI water and
glycerol.
Co40Fe40 B10Y10 (10–50 nm) Contact Angle (θ) with DI
Water as Test Liquid
Contact Angle (θ) with
Glycerol as Test Liquid
10 nm 78.1◦75.9◦
20 nm 78.0◦77.0◦
30 nm 76.8◦75.8◦
40 nm 72.9◦72.7◦
50 nm 71.7◦71.6◦
Coatings 2021,11, 250 11 of 14
Figure 8shows the surface energy of the CoFeBY films. As a consequence, it indicates
that the surface energy of as-deposited CoFeBY films was 24.4 mJ/mm
2
at 40 nm, which was
the highest value. When the annealing temperature was 100 and 200
◦
C, the best surface
energy of 50 nm was 25.59 mJ/mm
2
and 26.93 mJ/mm
2
, respectively. After annealing at
300
◦
C, the best surface energy was 31.07 mJ/mm
2
at 40 nm, as shown in Figure 8. This
result is consistent with SEM. When annealed at 300
◦
C for 40 nm, some defects can be
observed, which are caused by high surface energy. After heat treatment, the surface energy
of the film tended to become higher. With the increase of oxide content, the contact angle
decreases. Low contact angle corresponded to higher surface energy. When the film has
high surface energy, the adhesion is the strongest. These results show that it is easier to
combine with free layer and pinning layer of layered magnetic tunnel junctions.
Coatings 2021, 10, x FOR PEER REVIEW 11 of 14
Table 6. Average contact angles of CoFeBY nanofilms after annealing at 300 °C with DI water and
glycerol.
Co40Fe40B10Y10
(10–50 nm)
Contact Angle (θ) with DI Water
as Test Liquid
Contact Angle (θ) with
Glycerol as Test Liquid
10 nm 78.1° 75.9°
20 nm 78.0° 77.0°
30 nm 76.8° 75.8°
40 nm 72.9° 72.7°
50 nm 71.7° 71.6°
Figure 8 shows the surface energy of the CoFeBY films. As a consequence, it indi-
cates that the surface energy of as-deposited CoFeBY films was 24.4 mJ/mm2 at 40 nm,
which was the highest value. When the annealing temperature was 100 and 200 °C, the
best surface energy of 50 nm was 25.59 mJ/mm2 and 26.93 mJ/mm2, respectively. After
annealing at 300 °C, the best surface energy was 31.07 mJ/mm2 at 40 nm, as shown in
Figure 8. This result is consistent with SEM. When annealed at 300 °C for 40 nm, some
defects can be observed, which are caused by high surface energy. After heat treatment,
the surface energy of the film tended to become higher. With the increase of oxide con-
tent, the contact angle decreases. Low contact angle corresponded to higher surface en-
ergy. When the film has high surface energy, the adhesion is the strongest. These results
show that it is easier to combine with free layer and pinning layer of layered magnetic
tunnel junctions.
Figure 8. Surface energy of CoFeBY nanofilms.
3.5. Analysis of Optical Properties
Figure 9 shows the optical transmittance spectra of CoFeBY at visible wavelengths of
500 to 800 nm. In Figure 9a (CoFeBY at RT), the transmittance (%) decreased from 37 to
10.5%, as tf changed from 10 to 50 nm. In Figure 9b (CoFeBY after annealing at 100 °C), the
transmittance (%) decreased from 39.7 to 17%, when tf changed from 10 to 50 nm. In
Figure 9c (CoFeBY after annealing at 200 °C), the transmittance (%) decreased from 40 to
16.7%, as tf changed from 10 to 50 nm. In Figure 9d (CoFeBY after annealing at 300 °C),
the transmittance (%) decreased from 39.9 to 16%, when tf changed from 10 to 50 nm. The
transmittance of annealed samples was higher than that of RT samples. The addition of Y
and annealing could cause grain refinement [22]. With the increase of annealing temper-
ature, only a slight change in the transmittance could be observed, because the crystal
grain size did not change much, and the trend was not obvious. This result is in good
agreement with the average grain size measured by XRD. The result indicated that
thinner CoFeBY films have a higher transmission rate, because thicker films impeded the
Figure 8. Surface energy of CoFeBY nanofilms.
3.5. Analysis of Optical Properties
Figure 9shows the optical transmittance spectra of CoFeBY at visible wavelengths of
500 to 800 nm. In Figure 9a (CoFeBY at RT), the transmittance (%) decreased from 37 to
10.5%, as t
f
changed from 10 to 50 nm. In Figure 9b (CoFeBY after annealing at 100
◦
C),
the transmittance (%) decreased from 39.7 to 17%, when t
f
changed from 10 to 50 nm. In
Figure 9c (CoFeBY after annealing at 200
◦
C), the transmittance (%) decreased from 40 to
16.7%, as t
f
changed from 10 to 50 nm. In Figure 9d (CoFeBY after annealing at 300
◦
C),
the transmittance (%) decreased from 39.9 to 16%, when t
f
changed from 10 to 50 nm.
The transmittance of annealed samples was higher than that of RT samples. The addition
of Y and annealing could cause grain refinement [
22
]. With the increase of annealing
temperature, only a slight change in the transmittance could be observed, because the
crystal grain size did not change much, and the trend was not obvious. This result is
in good agreement with the average grain size measured by XRD. The result indicated
that thinner CoFeBY films have a higher transmission rate, because thicker films impeded
the signal of the incident light and result in decreased transmittance. It is confirmed that
the transmission of photons through the film is reduced due to the thickness effect and
interface effect of the film [43,44].
Coatings 2021,11, 250 12 of 14
Coatings 2021, 10, x FOR PEER REVIEW 12 of 14
signal of the incident light and result in decreased transmittance. It is confirmed that the
transmission of photons through the film is reduced due to the thickness effect and in-
terface effect of the film [43,44].
Figure 9. Transmittance of CoFeBY films. (a) RT, (b) after annealing at 100 °C, (c) after annealing at 200 °C, (d) after an-
nealing at 300°C.
4. Conclusions
Because of the addition of a suitable amount of Y in the alloys, the crystalline grain
size was reduced after the post-annealing treatment. When the thickness of CoFeBY
nanofilms increases from 10 to 50 nm, Ms tends to saturate, indicating the thickness effect
of MS on CoFeBY nanofilm. The MS was improved when the temperature in the
post-annealing process increased. The CoFeBY nanofilms were affected by size, and the
refinement of grains facilitated the ferromagnetic spin exchange coupling, thus increas-
ing the saturation magnetization. For the 300 °C annealed CoFeBY nanofilms, the max-
imum χac value was 0.165 at a 50 Hz fres, where the thickness of the films is 50 nm. The fres
values of the CoFeBY nanofilms in all thickness conditions were less than 500 Hz, signi-
fying that it could fulfill applications as the magnetic component in low-frequency sen-
sors. The 50-nm-thick film following annealing at 300 °C had the highest surface energy
in this work. It is worth mentioning that the strongest adhesion corresponded to the
highest surface energy. At the same time, the samples undergoing annealing showed that
the transmittance increased in comparison with the as-deposited films, because the av-
erage grain size became smaller after annealing, causing the transmittance to increase.
The results show that the thermal stability of CoFeB nanofilms can be improved by
adding appropriate amount of Y into CoFeB alloy, which indicates that the application of
rare earth materials in soft magnetic materials needs further development.
Author Contributions: Conceptualization, W.-J.L., Y.-H.C. and Y.-T.C.; Methodology, Y.-T.C.,
Y.-C.C., D.-Y.T.; Validation, Formal analysis, Y.-T.C. and P.-W.C.; Investigation, Y.-T.C. and
W.-J.L.; Resources, T.-H.W.; Writing—original draft preparation, Y.-T.C.; Writing—review and ed-
iting, Y.-T.C. and W.-J.L.; Supervision, Y.-T.C. and Y.-H.C.; Project administration, Y.-T.C. and
T.-H.W.; Funding acquisition, W.-J.L. and Y.-H.C. All authors have read and agreed to the pub-
lished version of the manuscript.
Figure 9.
Transmittance of CoFeBY films. (
a
) RT, (
b
) after annealing at 100
◦
C, (
c
) after annealing at 200
◦
C, (
d
) after
annealing at 300 ◦C.
4. Conclusions
Because of the addition of a suitable amount of Y in the alloys, the crystalline grain size
was reduced after the post-annealing treatment. When the thickness of CoFeBY nanofilms
increases from 10 to 50 nm, Ms tends to saturate, indicating the thickness effect of M
S
on
CoFeBY nanofilm. The M
S
was improved when the temperature in the post-annealing
process increased. The CoFeBY nanofilms were affected by size, and the refinement of
grains facilitated the ferromagnetic spin exchange coupling, thus increasing the saturation
magnetization. For the 300
◦
C annealed CoFeBY nanofilms, the maximum
χac
value was
0.165 at a 50 Hz f
res
, where the thickness of the films is 50 nm. The f
res
values of the CoFeBY
nanofilms in all thickness conditions were less than 500 Hz, signifying that it could fulfill
applications as the magnetic component in low-frequency sensors. The 50-nm-thick film
following annealing at 300
◦
C had the highest surface energy in this work. It is worth
mentioning that the strongest adhesion corresponded to the highest surface energy. At the
same time, the samples undergoing annealing showed that the transmittance increased in
comparison with the as-deposited films, because the average grain size became smaller
after annealing, causing the transmittance to increase. The results show that the thermal
stability of CoFeB nanofilms can be improved by adding appropriate amount of Y into
CoFeB alloy, which indicates that the application of rare earth materials in soft magnetic
materials needs further development.
Author Contributions:
Conceptualization, W.-J.L., Y.-H.C. and Y.-T.C.; Methodology, Y.-T.C., Y.-C.C.,
D.-Y.T.; Validation, Formal analysis, Y.-T.C. and P.-W.C.; Investigation, Y.-T.C. and W.-J.L.; Resources,
T.-H.W.; Writing—original draft preparation, Y.-T.C.; Writing—review and editing, Y.-T.C. and W.-J.L.;
Supervision, Y.-T.C. and Y.-H.C.; Project administration, Y.-T.C. and T.-H.W.; Funding acquisition,
W.-J.L. and Y.-H.C. All authors have read and agreed to the published version of the manuscript.
Funding:
This work was supported by the Ministry of Science and Technology, under Grant No.
MOST108-2221-E-224-015-MY3, MOST105-2112-M-224-001, and National Yunlin University of Science
and Technology, under Grant No. 110T06.
Coatings 2021,11, 250 13 of 14
Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is
not applicable to this article.
Conflicts of Interest:
The authors declare that there is no conflict of interests regarding the publication
of this paper. The funders had no role in the design of the study; in the collection, analyses, or
interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
References
1. Elmen, G.W. Magnetic alloys of iron, nickel, and cobalt. J. Frankl. Inst. 1929,207, 583–617. [CrossRef]
2.
Ogasawara, T.; Oogane, M.; Mahdawi, M.A.; Tsunoda, M.; Ando, Y. Effect of second-order magnetic anisotropy on non-linearity
of conductance in CoFeB/MgO/CoFeB magnetic tunnel junction for magnetic sensor devices. Sci. Rep. 2019,9, 1–9. [CrossRef]
3.
Devolder, T.; Couet, S.; Swerts, J.; Mertens, S.; Rao, S.; Kar, G.S. Effect of Tantalum Spacer Thickness and Deposition Con-ditions
on the Properties of MgO/CoFeB/Ta/CoFeB/MgO Free Layers. IEEE Mag. Lett. 2019,10, 1–4. [CrossRef]
4.
Honjo, H.; Ikeda, S.; Sato, H.; Nishioka, K.; Watanabe, T.; Miura, S.; Nasuno, T.; Noguchi, Y.; Yasuhira, M.; Tanigawa, T.; et al.
Impact of Tungsten Sputtering Condition on Magnetic and Transport Properties of Double-MgO Magnetic Tunneling Junction
With CoFeB/W/CoFeB Free Layer. IEEE Trans. Mag. 2017,53, 1–4. [CrossRef]
5.
Manos, O.; Bougiatioti, P.; Dyck, D.; Huebner, T.; Rott, K.; Schmalhorst, J.M.; Reiss, G. Correlation of tunnel magnetore-sistance
with the magnetic properties in perpendicular CoFeB-based junctions with exchange bias. J. Appl. Phys.
2019
,125, 1–6. [CrossRef]
6.
Lv, H.; Fidalgo, J.; Silva, A.V.; Leitao, D.C.; Kampfe, T.; Riedel, S.; Langer, J.; Wrona, J.; Ocker, B.; Freitas, P.P.; et al. Assessment of
conduction mechanisms through MgO ultrathin barriers in CoFeB/MgO/CoFeB perpendicular magnetic tunnel junctions. Appl.
Phys. Lett. 2019,114, 102402. [CrossRef]
7.
Iwata-Harms, J.M.; Jan, G.; Serrano-Guisan, S.; Thomas, L.; Liu, H.; Zhu, J.; Lee, Y.-J.; Le, S.; Tong, R.-Y.; Patel, S.; et al. Ultrathin
perpendicular magnetic anisotropy CoFeB free layers for highly efficient, high speed writing in spin-transfer-torque magnetic
random access memory. Sci. Rep. 2019,9, 1–7. [CrossRef] [PubMed]
8.
Ramazanov, M.A.; Maharramov, A.M.; Sultanova, C.R. Magnetoresistance effect in PP + Fe based nanocomposite system. Integr.
Ferroelectr. 2018,192, 141–145. [CrossRef]
9.
Albisetti, E.; Scaramuzzi, G.; Rinaldi, C.; Cantoni, M.; Bertacco, R.; Petti, D. Temperature dependence of the magnetic properties
of IrMn/CoFeB/Ru/CoFeB exchange biased synthetic antiferromagnets. Materials 2020,13, 387. [CrossRef]
10.
Sun, J.Z.; Trouilloud, P.L.; Lauer, G.P.; Hashemi, P. , Bias dependent conductance in CoFeB-MgO-CoFeB magnetic tunnel junctions
as an indicator for electrode magnetic condition at barrier interfaces. AIP Adv. 2019,9, 1–6. [CrossRef]
11.
Ota1, S.; Ono, M.; Matsumoto, H.; Ando, A.; Sekitani, T.; Kohno, R.; Iguchi, S.; Koyama, T.; Chiba, D. CoFeB/MgO-based
magnetic tunnel junction directly formed on a flexible substrate. Appl. Phys. Express 2019,12, 1–4. [CrossRef]
12.
Lee, D.-Y.; Hong, S.-H.; Lee, S.-E.; Park, J.-G. Dependency of Tunneling-Magnetoresistance Ratio on Nanoscale Spacer Thickness
and Material for Double MgO Based Perpendicular-Magnetic-Tunneling-Junction. Sci. Rep. 2016,6, 38125. [CrossRef]
13.
Rylkov, V.V.; Nikolaev, S.N.; Demin, V.A.; Emelyanov, A.V.; Sitnikov, A.V.; Nikiruy, K.E.; Levanov, V.A.; Presnyakov, M.Y.;
Taldenkov, A.N.; Vasiliev, A.L.; et al. Transport, magnetic, and memristive properties of a nanogranular (CoFeB)
x
(LiNbO
y
)
100−x
composite material. J. Exp. Theor. Phys. 2018,126, 353–367. [CrossRef]
14.
Sui, Y.; Liu, X.; Liu, C. Room temperature ferromagnetic property of Fe-Y (Fe: Y-6.5) composite oxide nano-cluster via an extremely
easy and scalable method. J. Rare Earths 2020. [CrossRef]
15.
Zhang, T.; Li, D. Effect of alloying yttrium on corrosion–erosion behavior of 27Cr cast white iron in different corrosive slurries.
Mater. Sci. Eng. A 2002,325, 87–97. [CrossRef]
16.
Luo, T.; Yang, Y.; Li, Y.; Dong, X. Influence of rare earth Y on the corrosion behavior of as-cast AZ91 alloy. Electrochim. Acta
2009
,
54, 6433–6437. [CrossRef]
17.
KSaksl; Bednarcˇcík, J.; Nicula, R.; Burkel, E.; Roth, S.; Franz, H. The influence of short-time ball-milling on the stability of
amorphous CoFeB alloys. J. Phys. Condens. Matter 2007,19, 1–14.
18.
Chrobak, A.; Nosenko, V.; Haneczok, G.; Boichyssyn, L.; Karolus, M.; Kotur, B. Influence of rare earth elements on crystal-lization
of Fe82Nb2B14RE2 (RE = Y, Gd, Tb, and Dy) amorphous alloys. J. Non Cryst. Solids. 2011,357, 4–9. [CrossRef]
19.
Chrobak, A.; Nosenko, V.K.; Haneczok, G.; Boichyshyn, L.; Kotur, B.; Bajorek, A.; Životský, O.; Hendrych, A. Effect of rare earth
additions on magnetic properties of Fe82Nb2B14RE2 (RE = Y, Gd, Tb and Dy) amorphous alloys. Mater. Chem. Phys.
2011
,130,
603–608. [CrossRef]
20.
Mao, Y.; Zhu, Z.; Zhao, H. Microstructures and soft magnetic properties of Fe
73.5
Cu
1
Nb
3−x
Si
13.5
B
9
Y
x
(x= 0–1.5) alloys. J. Rare
Earths 2020. [CrossRef]
21.
Fan, X.; Chen, K.; Guo, S.; Chen, R.; Lee, D.; Yan, A.; You, C. Core-shell Y-substituted Nd-Ce-Fe-B sintered magnets with enhanced
coercivity and good thermal stability. Appl. Phys. Lett. 2017,110, 1–4. [CrossRef]
22.
Zhang, C.H.; Luo, Y.; Yu, D.B.; Quan, N.T.; Wu, G.Y.; Dou, Y.K.; Hu, Z.; Wang, Z.L. , Permanent magnetic properties of Nd–Fe–B
melt-spun ribbons with Y substitution. Rare Metals 2020,39, 55–61. [CrossRef]
23.
Huang, X.M.; Wang, X.D.; Jiang, J.Z. Origin of high glass forming ability of Y- containing FeB-based alloys. J. Alloys Compd.
2009
,
485, L35–L38. [CrossRef]
24.
Liu, S.; Cao, Q.; Wang, X.; Zhang, D.; Su, Q.; Du, G.; Jiang, J. Effects of thickness on structure and magnetic property of Fe-Y-B
thin films. Thin Solid Films 2016,616, 608–617. [CrossRef]
Coatings 2021,11, 250 14 of 14
25.
Jimbo, M.; Komiyama, K.; Shirota, Y.; Fujiwara, Y.; Tsunashima, S.; Matsuura, M. Thermal stability of spin valves using amorphous
CoFeB. J. Magn. Magn. Mater. 1997,165, 308–311. [CrossRef]
26.
Ma, K.; Chung, T.S.; Good, R.J. Surface energy of thermotropic liquid crystalline polyesters and polyesteramide. J. Polym. Sci.
1998,36, 2327–2337. [CrossRef]
27. Owens, D.K.; Wendt, R.C. Estimation of the surface free energy of polymers. J. Appl. Polym. Sci. 1969,13, 1741–1747. [CrossRef]
28.
Kaelble, D.H.; Uy, K.C. A Reinterpretation of Organic Liquid-Polytetrafluoroethylene Surface Interactions. J. Adhes.
1970
,2, 50–60.
[CrossRef]
29.
Chen, Y.-T.; Chang, C. Effect of grain size on magnetic and nanomechanical properties of Co60Fe20B20 thin films. J. Alloy. Compd.
2010,498, 113–117. [CrossRef]
30.
Liu, T.; Shen, H.; Wang, C.; Chou, W. Structure evolutionofY2O3 nanoparticle/Fe composite during mechanicalmillin-
gandannealing. Prog. Nat. Sci. 2019,23, 434–439. [CrossRef]
31. Cullity, B.D.; Weymouth, J.W. Elements of X-Ray Diffraction. Am. J. Phys. 1957,25, 394–395. [CrossRef]
32.
Jen, S.U.; Yao, Y.D.; Chen, Y.T.; Wu, J.M.; Lee, C.C.; Tsai, T.L.; Chang, Y.C. Magnetic and electrical properties of amorphous CoFeB
films. J. Appl. Phys. 2006,99, 053701. [CrossRef]
33.
Noce, R.D.; Benedetti, A.V.; Magnani, M.; Passamani, E.C.; Kumar, H.; Cornejo, D.R.; Ospina, C.A. , Structural, morpho-logical
and magnetic characterization of electrodeposited Co–Fe–W alloys. J. Alloys Compd. 2014,611, 243–248. [CrossRef]
34. R. C. O’Handley. Modern Magnetic Materials; J. Wiley & Sons Inc.: New York, NY, USA, 2000.
35.
Yang, S.; Chieh, J.; Wang, W.; Yu, C.; Hing, N.; Horng, H.; Hong, C.-Y.; Yang, H.; Chang, C.; Lin, H. Magnetic nanoparticles for
high-sensitivity detection on nucleic acids via superconducting-quantum-interference-device-based immunomagnetic reduction
assay. J. Magn. Magn. Mater. 2011,323, 681–685. [CrossRef]
36.
Chen, Y.T.; Xie, S.M.; Jheng, H.Y. The low-frequency alternative-current magnetic susceptibility and electrical properties of
Si(100)/Fe
40
Pd
40
B
20
(X Å)/ZnO(500 Å) and Si(100)/ZnO(500 Å)/Fe
40
Pd
40
B
20
(Y Å) systems. J. Appl. Phys.
2013
,113, 1–3.
[CrossRef]
37.
Zhang, J.; Li, Y.-X.; Wang, F.; Shen, B.-G.; Sun, J.-R. Coercivity mechanism of nanocomposite Sm-Co/Fe multilayer films. J. Appl.
Phys. 2010,107, 43911. [CrossRef]
38.
Bendavid, A.; Martin, P.; Wieczorek, L. Morphology and optical properties of gold thin films prepared by filtered arc deposition.
Thin Solid Films 1999,354, 169–175. [CrossRef]
39.
Xu, S.T.; Ma, Y.Q.; Zheng, G.H.; Dai, Z.X. Simultaneous effects of surface spins: Rarely large coercivity, high remanence
magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles. Nanoscale 2015,7, 6520–6526. [CrossRef]
40.
Muroi, M.; Street, R.; McCormick, P.G.; Amighian, J. Magnetic properties of ultrafine MnFe2O4 powders prepared by
mechanochemical processing. Phys. Rev. B 2001,63, 1–7. [CrossRef]
41.
Jonsson, T.; Nordblad, P.; Svedlindh, P. Dynamic study of dipole-dipole interaction effects in a magnetic nanoparticle system.
Phys. Rev. B 1997,57, 497–504. [CrossRef]
42.
Kong, S.H.; Okamoto, T.; Nakagawa, S. [Ni-Fe/Si] double seedlayer with low surface energy for Fe-Co-B soft magnetic underlayer
with high Hk for perpendicular magnetic recording media. IEEE Trans. Magn. 2004,40, 2389–2391. [CrossRef]
43.
Tavakoli, M.M.; Dastjerdi, H.T.; Zhao, J.; Shulenberger, K.E.; Carbonera, C.; Po, R.; Cominetti, A.; Bianchi, G.; Klein, N.D.;
Bawendi, M.G.; et al. Light Management in Organic Photovoltaics Processed in Ambient Conditions Using ZnO Nanowire and
Antireflection Layer with Nanocone Array. Small 2019,15, e1900508. [CrossRef] [PubMed]
44.
Erdem, T.; Yang, L.; Xu, P.; Altıntas, Y.; O’Neil, T.; Caciagli, A.; Ducati, C.; Mutlugun, E.; Scherman, O.A.; Eiser, E.; et al.
Transparent Films Made of Highly Scattering Particles. Langmuir 2020,36, 911–918. [CrossRef] [PubMed]
