Haein Choi-Yim

Haein Choi-Yim
Sookmyung Women's University · Department of Nano Physics

PhD

About

97
Publications
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2,399
Citations
Additional affiliations
September 2005 - present
Sookmyung Women's University
Position
  • Professor (Full)
January 1999 - August 2005
California Institute of Technology
Position
  • Senior Researcher

Publications

Publications (97)
Article
Full-text available
The soft magnetic amorphous ribbons of (FexCo1−x)85M9Nb1B5 (M = Zr or Hf, x = 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) were investigated in this study. Replacing Zr by Hf turned out to increase saturation magnetization and, at the same time, reduce the coercivity, both of which serve together in enhancing the soft magnetic performance of the alloys. Moreo...
Article
Full-text available
In the Fe-Co alloy system, the addition of Cr improves the glass-forming ability (GFA) with superior soft magnetic properties such as high saturation magnetization (Ms) and low coercivity (Hc). In addition, Cr is considered to be an important factor for improving the corrosion resistance of Fe-based amorphous alloy. Therefore, in the present study,...
Article
Full-text available
To increase the saturation magnetization (Ms) of commercially available soft magnetic Finemet alloys to the level comparable to that of Si-steel and Fe-based nanocrystalline alloys such as Nanoperm, Nanomet, the B or Si content in combination with annealing heat treatment was tailored. The ribbons of Fe95−xSi1BxNb3Cu1 (x = 11, 12, 13) and Fe87−xSix...
Article
In the present study, the magnetic and microstructural properties were investigated of Fe-based nanocrystalline soft magnetic alloy with the composition of Fe80Si7B9Nb3Cu1 fabricated by the melt-spinning method. The annealing under varying transverse magnetic field was applied to induce the uniform distribution of α-Fe nanocrystals. The lowest core...
Article
In the present study, we investigated the effect of heat treatment on the magnetic properties of the Fe87-xSixB9Nb3Cu1 (x = 1, 3, 5, 7, 9, and 13.5) alloy system. Ribbon samples with the width of 2 mm and thickness of 20–30 μm were synthesized by melt spinning. Among the samples, only amorphous samples were nanocrystallized by annealing between 360...
Article
Full-text available
We have investigated electrical properties of a ribbon-shaped iron-based magnetic amorphous alloy Fe 85-x Co x Ti 7 Hf 6 B 2 x = 20 30 35 which were fabricated by a single copper roller vacuum melt-spinning technique. It has been found that their saturation magnetization was similar to that of other FeCo-based alloys and had a maximum value when th...
Article
The rare-earth-free hard magnetic L1 0 -FeNi phase found in cosmic meteorites demonstrates potential as a next-generation permanent magnet. However, it is very difficult to artificially produce the L1 0 -FeNi phase due to the low atomic diffusion coefficients of Fe and Ni near the order-disorder transition temperature (∼320 °C). Therefore, FeNiPC a...
Article
The viscous thermal flow behavior and mechanical property of [Fe0.6Co0.15B0.2Si0.05] (100−x)Tax (x = 0, 1, 2, 3, 4, and 5) soft magnetic amorphous ribbons were studied. The characteristics of melt-spun amorphous ribbons were measured by using vibration sample magnetometer (VSM), nanoindentation, differential scanning calorimetry (DSC) and thermo-me...
Article
The effects of Fe content on the thermal, magnetic, and mechanical properties of a Co72B19.2Si4.8Mo4 alloy were studied. Amorphous soft magnetic alloys of (Co1−xFex)72 B19.2Si4.8Mo4 (0 ≤ x ≤ 1) with 3-mm widths and 27 - 30 μm thicknesses were obtained by using the melt spinning technique. The crystallization temperature (Tx) for each alloy was meas...
Article
Soft magnetic materials are ubiquitously utilized in various applications such as motors, actuators, sensors, and so forth. The requirements for efficient cores in electric power transmission devices include low core loss and high saturation magnetization. Here we report the magnetic properties of Fe-based soft magnetic alloys with the compositions...
Article
The annealing effects on the magnetic properties of the Co72B19.2Si4.8Cr4 and Co64.8Fe7.2B19.2Si4.8Cr4 alloy systems are reported. Ribbon samples with 2 mm width and 20–30 μm thickness for both compositions were synthesized by melt spinning. The as-spun samples were subjected to annealing at various temperatures below their glass transition tempera...
Article
Perpendicular magnetic thin films are one of the most attractive systems for application in the industry of next-generation devices. In order to apply a next-generation device, a perpendicular magnetic multilayer must have a large magnetic anisotropy and a low saturation magnetization. In addition, the demagnetizing field of the multilayer inhibits...
Article
We studied the thermal and the magnetic properties of (Co1−xFex)72B19.2Si4.8Ta4 (0 ≤ x ≤ 1.0) alloy ribbons. These Co-based and Fe-based melt-spun ribbons were produced by using an arc-melting furnace and the melt-spinning technique. X-ray diffraction (XRD) peaks indicated that the ribbons had both an amorphous phase and a partial crystalline phase...
Article
The effect of the Si additions on the magnetic properties is reported for the novel Fe87-xTi7Zr6Six (x = 0, 2, 4, 6, 8, 10) alloy system. The 2 mm wide ribbon samples for each composition were prepared by the melt spinning technique, and their phase information and magnetic behavior were obtained from X-ray diffraction and a vibrating sample magnet...
Article
CoSiB is the amorphous ferromagnetic material and multilayer consisting of CoSiB and Pd has perpendicular magnetic anisotropic property. PMA has strong advantages for STT-MRAM. Moreover, amorphous materials have two advantages more than crystalline materials: no grain boundary and good thermal stability. Therefore, we studied the magnetic propertie...
Article
The effect of the B additions on glass formation and magnetic properties is reported for the Fe(87-x-y)CoyTi7Zr6Bx (x = 2, 4, 6 and y = 35, 40) alloy system. The ribbon samples with the width of 2 mm for each composition were prepared by the melt spinning technique; furthermore, their phase information was obtained from X-ray diffraction. Glass for...
Article
Full-text available
High-performance magnetic materials have immense industrial and scientific importance in wide-ranging electronic, electromechanical, and medical device technologies. Metallic glasses with a fully amorphous structure are particularly suited for advanced soft-magnetic applications. However, fundamental scientific understanding is lacking for the spin...
Article
The ratios of Fe/Co and Fe/B in a ferromagnetic alloy system, Fe(87− x − y ) Co x Ti7 Zr6 By (x = 20, 30, and 40 at% and y = 2 and 4 at%), which was produced by the melt-spinning technique in the form of thin ribbons, were investigated to improve the saturation magnetization. The thermal properties Tx were in the range of 792.0 K to 838.0 K, and it...
Article
We investigated a soft magnetic Fe(87-x-y)CoxTi7Zr6By (x = 25, 30, 35 at.%, and y = 2, 4 at.%) alloy system. The Fe-based amorphous materials have been studied because of excellent soft magnetic properties: high saturation magnetization and low coercivity. Especially, the Fe-Co system has the high saturation magnetization in comparison to Fe-only a...
Article
Full-text available
The magnetic properties of CoSiB/Pd multilayers were prepared by a DC sputtering system have been investigated using a vibrating sample magnetometer. We investigated the magnetic properties of CoSiB/Pd multilayers for various CoSiB thicknesses in a previous article. Based on those data, the CoSiB thickness was kept constant at 7 Å while the Pd thic...
Article
We examined the effect of the substitution of Fe atoms for Co atoms iron on the thermal and the magnetic properties for (Co1−x Fex )72B19.2Si4.8Cr4 (0 ≤ x ≤ 1) system. We made ribbons with diameters of 2 mm by using melt spinning technique. The broad X-ray diffraction pattern without any crystalline peaks indicates the fully amorphous structure for...
Article
Full-text available
We investigate the magnetic properties of CoSiB (15-Å-thickness)/Pd (Pd thickness = 8, 11, 14, 17, 20, 24, 27, 29 and 33 Å)/CoSiB (15-Å-thickness) trilayer thin films. The CoSiB-layer thickness was fixed to 15 Å, while the Pd-layer thickness was varied from 8–33 Å. In this paper, we present a new type of thin film containing amorphous Co75Si15B10 a...
Article
Full-text available
Spin transfer torque (STT) induced switching of magnetization has led to intriguing and practical possibilities for magnetic random access memory (MRAM). This form of memory, called STT-MRAM, is a strong candidate for future memory applications. This application usually requires a large perpendicular magnetic anisotropy (PMA), large coercivity, and...
Article
We investigated the perpendicular magnetic anisotropy and the Hall resistivity of CoSiB/Pd multilayers. The CoSiB/Pd multilayers consisted of CoSiB (7-Å thickness) and Pd (Pd thickness tPd = 10, 12, 14, 16, 18, and 20 Å), and a CoSiB/Pd bilayer was stacked five times. The coercivity shows oscillating values between tPd = 12 Å and tPd = 20 Å. The va...
Article
Full-text available
Thermal and magnetic properties of a recently developed metallic glass of four different compositions [{Co(1−x)Fe(x)}(0.75)B(0.2)Si(0.05)]96Cr4 were evaluated, where x = 0, 0.1, 0.2, and 0.3. Coercivity decreased and saturation magnetization increased with the increase in iron content. All alloys showed a high Curie temperature. The trend in therma...
Article
The effect of cooling rate on the thermal stability and soft magnetic properties of [(Fe0.5Co0.5) 0.75B0.2Si0.05]100-xNbx (x = 5, 6, 7, 8 at. %) system was investigated. The alloys were produced into the form of ribbon and cylindrical rod by melt-spinning and injection casting, respectively. Their structure, thermal, mechanical and soft magnetic pr...
Article
Full-text available
The perpendicular magnetic anisotropic property of amorphous CoSiB/Pd multilayers was studied as a function of the thicknesses of the CoSiB and the number of repeated CoSiB/Pd bilayers. In this study, we investigate the effects of thermal annealing on the perpendicular magnetic anisotropic property of the [CoSiB 2, 3, 4, 5 Å/Pd 13 Å]5 multilayer fi...
Article
The effect of the replacement of Fe by Co or B on the thermal stability and soft magnetic properties of the Fe-based amorphous metallic ribbons with Fe(87-x-y) Cox Ti7 Zr6 By (x = 10, 20% and y = 8, 10, 12 %) produced by melt-spinning technique was investigated. For the melt-spun amorphous ribbons, the values of saturation magnetization and coerciv...
Article
The perpendicular magnetic anisotropy (PMA) of amorphous CoSiB/Pt multilayer systems was studied as a function of the thickness of the CoSiB/Pt bilayer and the number of repeated CoSiB/Pt bilayers. In this letter, we investigate the thermal property of a CoSiB single layer film annealed at 150 ∼ 350 °C for 3 hours and the perpendicular magnetic ani...
Article
Systematic investigation on thermal and mechanical properties of Cu60−xZr25Ti15Nix bulk metallic glasses with x = 0, 1, 3, 5, 7, 9 and 11 at.% points out that monolithic Cu53Zr25Ti15Ni7 and Cu51Zr25Ti15Ni9 bulk metallic glasses containing optimum Ni content of 7 and 9 at.% are effective to enhance both thermal stability of amorphous structure up to...
Article
The soft magnetic Fe-based amorphous metallic ribbons Fe(87−x)Ti7Zr6[Bx Six ]0.5 (x = 8, 10, 12%) were prepared using the melt-spinning technique to have thickness of 15–22 μm and widths of 1-2 mm. Increasing the amounts of B and Si improved the soft magnetic properties: the coercivity (H c) decreased, and the saturation magnetization (M S) increas...
Article
Full-text available
The metallic glass ribbons of (x = 0, 0.3, 0.6, 0.9 at.%) and (x = 0, 0.3, 0.6, 0.9 at.%) were obtained by melt spinning with 25-30 thickness. The thermal stability, mechanical properties and magnetic properties of Fe-Co-B-Si based systems were investigated. The values of thermal stability were measured using differential scanning calorimetry (DSC)...
Article
Perpendicular magnetic anisotropy (PMA) is the phenomenon of magnetic thin film which is preferentially magnetized in a direction perpendicular to the film`s plane. Amorphous multilayer with PMA has been studied as the good candidate to realization of high density STT-MRAM (Spin Transfer Torque-Magnetic Random Access Memory). The current issue of h...
Article
Full-text available
We investigated the perpendicular magnetic anisotropy of amorphous CoSiB/Pd multilayer systems. We replaced the crystalline Co layer with an amorphous CoSiB layer in a Co/Pd multilayer system in order to reduce the domain wall pinning sites, which are mainly located at the grain boundaries and interfaces. We also found the correlation between the c...
Article
Established in 2002 as a result of the first IUPAP International Conference on Women in Physics, and subsequently ratified as one of the permanent committees in the Korean Physical Society (KPS), the Women in Physics Committee in Korea has been playing a central role in making society aware of improvement of women's status through a variety of effo...
Article
The ferromagnetic amorphous alloys Co-Fe-B-Si-Cr and Co-Fe-B-Si-Ta were systemically investigated. [(Co1−x Fex )0.75B0.2Si0.05]96Cr4 (x = 0, 0.1, 0.4, 0.7, 1.0) and [(Co1−x Fex )0.75B0.2Si0.05]96Ta4 (x = 0, 0.1, 0.3, 0.5, 1.0) ribbons were prepared by using the melt-spinning technique. Amorphous structures were confirmed by the presence of a broad...
Article
Perpendicular magnetic anisotropy has been studied for possible use in high-density spin transfer torque magnetic random access memories. The key issues of high-density spin transfer torque magnetic random access memories are decreasing the switching current and have the high thermal stability. In order to solve these problems, the approach of deve...
Article
In this letter, we report the perpendicular magnetic anisotropy of [CoSiB tCoSiB nm/Pd 1.3 nm]5 multilayer for tCoSiB equal to 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 nm and of [CoSiB 0.3 nm/Pd tPd nm]5 multilayer for tPd equal to 1.1, 1.2, 1.3, 1.4, 1.5, and 1.6 nm. We also presented to for [CoSiB 0.3 nm/Pd 1.3 nm]n multilayer for n equal to 3, 5, 7, 9, 1...
Article
The ferromagnetic metallic glass alloys in the Co-Fe-B-Si-Nb system were investigated. Such glassy alloys exhibit high glass-forming ability (GFA), as well as good mechanical and magnetic properties. Based on those results, [(Co0.5Fe0.5)0.75B0.2Si0.05]100−x Nbx (x = 5, 6, 7, 8 at.%) were chosen for this investigation with increasing Nb contents. Am...
Article
Perpendicular magnetic anisotropy is being widely studied as a possible candidate for a high-density spin-transfer torque magnetic random access memory. The key issues of a high-density spin-transfer torque magnetic random access memory are decreasing the switching current and the high thermal stability. In order to solve these problems, two approa...
Article
The ferromagnetic metallic glass alloys in the Co-Fe-B-Si-M (M = Mo or Nb) system were investigated. Ingots of [(Co1−x Fex )0.75B0.2Si0.05]96Mo4 (x = 0, 0.2, 0.5, 0.8, 1.0) and [(Co1−x Fex )0.75 B0.2Si0.05]96Nb4 (x = 0, 0.2, 0.5, 0.8, 1.0) alloys were cast into about 30 µm-thick ribbons by using a melt spinning method. As-spun ribbons were identifi...
Article
Stable bulk glass forming alloys can be developed over a wide range of compositions in the Cu-Hf-Al ternary system. The compositional and the cooling rate dependences of the thermal and the elastic properties of Cu-Hf-Al alloys were systematically investigated. Evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The gla...
Article
We have investigated the perpendicular magnetic anisotropy of a [CoSiB t(CosiB)/Pt 14 angstrom](5) multilayer as a function of the CoSiB thickness. We have studied the perpendicular magnetic anisotropy of [Co t(Co)/Pt 15 angstrom](5) and [CoFe t(CoFe)/Pt 10 angstrom](5) multilayers for various thicknesses of Co and Co Fe. Furthermore, we have measu...
Article
The metallic glass {(Fe1-xCox)(0.75) B0.2Si0.05}(96)Nb-4 (x = 0 similar to 0.9) system was studied. One of these systems, {Fe1-xCox)(0.75) B0.2Si0.05}(96)Nb-4 (x = 0.5), has the highest glass-forming ability (GFA). We made Co36Fe36B19.2Si4.8Nb4 into ribbon with a thickness of 0.03 mm, strips with thicknesses of 1 mm, 2 mm, and 3 mm and rods with di...
Article
Bulk metallic glass matrix composites are processed and investigated by X-ray diffraction, DSC, optical microscopy, SEM, microprobe, TEM, and mechanical testing. Ceramics such as SiC, WC, or TiC, and the metals W or Ta are introduced as reinforcements into the metallic melt. The metallic glass matrix remains amorphous after adding up to 30 vol% of...
Article
Magnetic anisotropy properties of amorphous ferromagnetic CoSiB/Pt multilayers with perpendicular magnetic anisotropy (PMA, K(u)) were systematically investigated as a function of CoSiB layer thickness (t(coSiB)) and Pt layer thickness (t(Pt)). In two series of [CoSiB t(coSiB)Pt t(P1)]5 multilayers, the perpendicular coercivity (H(c)) increased to...
Article
We have investigated the perpendicular magnetic anisotropy of [CoSiB t(CoSiB)/Pt t(Pt)](n) multilayers as a function of the CoSiB and the Pt thicknesses and the number of repetition of the CoSiB/Pt bilayers. The coercivity (H(c)) and the saturation magnetization (M(s)) of the amorphous ferromagnetic material Co(75)Si(15)B(10) were taken to be 1.6 O...
Article
A magnetic tunnel junction (MTJ) with a Co2FeAl0.5Si0.5 (CFAS) heusler film on a conductive Ta/Ru buffer layer was fabricated for the first time. In the as-deposited state, a highly B2-ordered CFAS film was obtained by using the Ta/Ru buffer layer. The Ta (110) buffer layer causes a Ru (002) buffer layer, which leads to the growth of CFAS with a B2...
Article
Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3–6 mm. The evidence of the amorphou...
Article
The magnetic and thermal properties of Co<sub>70.5</sub>Fe<sub>4.5</sub>Si1<sub>5</sub>B<sub>10</sub> and Ni<sub>16</sub>Fe<sub>62</sub>Si<sub>8</sub>B<sub>14</sub> quaternary amorphous alloys (metallic glasses) used for a free layer in the magnetic tunnel junctions (MTJs) were studied to correlate magnetic and glass characterization of amorphous a...
Article
Full-text available
The three kinds of double-barrier magnetic tunnel junction (DMTJ) with or without amorphous ferromagnetic Co<sub>70.5</sub>Fe<sub>4.5</sub>Si<sub>15</sub>B<sub>10</sub> (in at. %) free-layer were investigated to understand the effect of the free-layer on the bias voltage dependence of tunneling magnetoresistance (TMR) ratio. The DMTJ structure cons...
Article
The Cu{sub 49}Hf{sub 42}Al{sub 9} bulk metallic glass with a critical diameter of 10 mm was recently developed by J. Xu et al. We attempted to reproduce this alloy and developed Cu-Hf-Al ternary systems. The maximum critical diameter of the new bulk glassy alloy was 6 mm. The width of the supercooled liquid region {delta}Tx = Tx-Tg for this glass w...
Article
The Korean Physical Society (KPS) Women Committee has organized a series of the physics camps for high school girl students to give them an opportunity to work together and interact with professional physicists. Although the KPS Women Committee has successfully set the KPS's face toward women's issues, it still needs more systematic support for hel...
Article
Ferromagnetic CoFeSiB and NiFeSiB metallic glasses were produced to study the thermal and magnetic properties of glassy alloys which show the good performance for free layers in the Magnetic tunnel junctions (MTJs). The characters of amorphous materials are compared with crystalline materials composed of CoFe and NiFe. X-ray diffraction pattern was...
Article
Stable bulk metallic glasses can be found over in the neighborhood of Cu50Hf45Al5 and Cu60Hf 25Ti15. The thermal and the mechanical properties of the Cu-Hf-Al and the Cu-Hf-Ti systems are examined. Cu-Hf-Al alloys have a strength of ∼2 GPa, a Tg of ∼500 °C and a ΔT of ∼80 °C. On the other hand, Cu-Hf-Ti alloys have a Tg of ∼450 °C and a ΔT of ∼50 °...
Article
Full-text available
A synthetic antiferromagnet (SAF) structure comprising two ferromagnetic amorphous CoFeSiB layers was employed as a free layer in magnetic tunnel junctions (MTJs) to enhance magnetotransport and magnetization switching performance. In Si-SiO<sub>2</sub>/Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlO<sub> x </sub>1.5/CoFeSiB t (t=3.5 , 4.0, 4.5, 5.0)/Ru 1.0/CoFeSi...
Article
We report in-situ composite formation in NiCuTiZrSi and NiCuTiZr alloys. The X-ray diffraction patterns of the alloys show a primary Ni(Ti,Zr) B2 structure superimposed on the diffuse scattering maximum from the amorphous phase. The microstructure of the composites was investigated with scanning electron microscopy and transmission electron microsc...
Article
The angular dependence of the exchange bias(H_{ex}) and coercivity(H_c) in multilayer [Pt/Co]_N-IrMn with applied measuring field rotated toward in-plane at angle \theta from perpendicular-to-plane, has been measured. Multilayer films consisting of Si/SiO_2/Ta(50)/Pt(4)/[Pt(15)/Co(t_{Co})]_N/IrMn(50)/Ta(50)(in\;{\AA}) were prepared by magnetron spu...
Article
Double-barrier magnetic tunnel junctions (DMTJs) with and without an amorphous ferromagnetic material such as CoFeSiB 10, CoFe 5/CoFeSiB 5, and CoFe 10 (nm) were prepared and compared to investigate the bias voltage dependence of the tunneling magnetoresistance (TMR) ratio. Typical DMTJ structures were Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlOx /free layer 1...
Article
Full-text available
This study examined the structural, magnetic, and transport properties of CoFeSiB films with various Co compositions. The main focus was on two samples, amorphous Co<sub>74</sub>Fe<sub>4</sub>Si<sub>14</sub>B<sub>8</sub> and nanocrystalline Co<sub>78</sub>Fe<sub>2</sub>Si<sub>12</sub>B<sub>8</sub> thin films. The results show that the amorphous fil...
Article
Good bulk glass forming alloys can be found over a wide range of compositions in the neighborhood Of CU60Hf25Ti15. The glass forming ability, thermal and mechanical properties of the Cu-Hf-Ti system is examined for alloys in the composition range of 57.5 < Cu < 62.5, 22.5 < Hf < 28.75, 11.25 < Ti < 17.5 (at.%). These alloys typically have strength...
Article
In this study, 80% volume fraction (vf) composites were fabricated with 0.25 mm Mo or Ta wire combined with Zr57Nb5Al10Cu15.4Ni12.6 bulk metallic glass. Quasistatic compression and tension tests were performed. Neutron diffraction was used to measure in situ internal reinforcement strains inside the composites during compressive loading. The compos...
Article
The newly discovered Ni–Nb–Sn glass is considered a promising refractory material due to its high glass transition temperature (Tg>880K). An adequate oxidation resistance at high temperatures is therefore necessary. In this paper the oxidation behavior of the Nb35Ni60Sn5 refractory alloy glass has been studied in dry air in the temperature range of...
Article
Ternary Ni_(60)Nb_(40−x)Sn_x (3 ≤ x < 9 at.%) and quaternary Ni_(60)(Nb_(100−x)Ta_x)_(34)Sn_6 (x = 20, 40, 60 and 80 at.%) Ni-base alloys were found to form bulk amorphous structures using conventional metallic-mold casting. These bulk amorphous alloys have very high glass transition temperatures (881 K < T_g < 895 K). They also exhibit high Young'...
Conference Paper
Full-text available
The newly discovered Ni–Nb–Sn glass is considered a promising refractory material due to its high glass transition temperature (T_g > 880 K). An adequate oxidation resistance at high temperatures is therefore necessary. In this paper the oxidation behavior of the Nb_(35)Ni_(60)Sn_5 refractory alloy glass has been studied in dry air in the temperatu...
Conference Paper
In this study, we investigated that both magnetic switching and tunneling magnetoresistance (TMR) ratio of MTJs with the NiFeSiB free layer. The junctions were fabricated by a photolithographic patterning procedure and ion beam etching. A magnetic field of 100 Oe was applied during deposition to induce the uniaxial magnetic anisotropy in ferromagne...
Article
Systematic investigations of the microstructure of Ni50Ti33Zr16Si1, Ni45Cu5Ti33Zr16Si1 and Ni40Cu10Ti33Zr16Si1 slowly cooled bulk specimens reveal the local occurrence of an amorphous phase in these alloys. The sites and the morphology of the amorphous phase strongly depend on the presence of Cu. The formation of a nanoscale amorphous phase in the...
Article
Refractory bulk metallic glasses and bulk metallic glass composites are formed in quaternary Ni–Nb–Ta–Sn alloy system. Alloys of composition Ni60(Nb100−xTax)34Sn6 (x = 20, 40, 60, 80) alloys were prepared by injection-casting the molten alloys into copper molds. Glassy alloys are formed in the thickness of half mm strips. With thicker strips (e.g.,...
Article
To obtain low switching field (Hsw) we introduced amorphous ferromagnetic Co70.5Fe4.5Si15B10 single and synthetic antiferromagnet (SAF) free layers in magnetic tunnel junctions (MTJs). The switching characteristics for MTJs with structures Si/SiO2/Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlOx/CoFeSiB 7 or CoFeSiB (t)/Ru 1.0/CoFeSiB (7−t)/Ru 60 (in nanometer) we...
Article
Ternary alloys of composition Ni60Nb40−xSnx, with 3 ⩽ x < 9, were found to form bulk metallic glasses. These alloys exhibit a high elastic modulus and measured compressive yield strength between 1.8 and 2.8 GPa. The measured yield strength of these ternary alloys depends strongly on their Sn content and is generally lower than the strength estimate...
Article
In situ composites were synthesized by arc melting Ni–(Cu)–Ti–Zr–Si alloys. The X-ray diffraction patterns of rapidly cooled cast strips show a primary Ni(Ti, Zr) B2 structure superimposed on the diffuse scattering maxima from the amorphous phase. Compression test results show that the composite starts to yield at 1200 MPa and fractures at 1900 MPa...
Article
Full-text available
We report on experimental evidence for local amorphization∕nanocrystallization at the interfaces between the B2-ordered Ni(Ti,Zr) phase and the NiTiZr phase with P63∕mmc during solidification of a multicomponent Ni45Cu5Ti33Zr16Si1 alloy. So far there are several well-known mechanisms for interfacial amorphization in the solid state but no interfaci...
Article
We report on experimental evidence for local amorphization/nanocrystallization at the interfaces between the B2-ordered Ni(Ti,Zr) phase and the NiTiZr phase with P63/mmc during solidification of a multicomponent Ni45Cu5Ti33Zr16Si1 alloy. So far there are several well-known mechanisms for interfacial amorphization in the solid state but no interfaci...
Article
Bulk metallic glasses (BMGs) possess a unique set of mechanical properties that make them attractive structural materials. However, when loaded without constraint, BMGs fracture catastrophically due to formation of macroscopic shear bands and this behavior reduces their reliability. To address this issue, BMG matrix composites have been developed....