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ABSTRACT: Magnetic ordering of Dy(3+) ion in low-dimensional magnet CsDy(WO4)2, (CsDyW) has been first studied by means of measurements of the low temperature specific heat over a temperature range of 0.5-23 K. The ordering temperature (T(sub N)) of the Dy(3+) sublattice was established to be 1.34 K. The experimental data indicate on the antiferromagnetic (AFM) character of Dy(3+) ions interactions. The magnetic behavior above and below T(sub N) is discussed in the framework of different theoretical models.
11/2012;
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ABSTRACT: Magnetic and electron paramagnetic resonance (EPR) properties of
EuFe3(BO3)4 single crystals have been studied over the
temperature range of 300–4.2K and in a magnetic field up to 5T. The
temperature, field and orientation dependences of susceptibility,
magnetization and EPR spectra are presented. An antiferromagnetic ordering
of the Fe subsystem occurs at about 37K. The easy direction of
magnetization perpendicular to the c axis is determined by magnetic
measurements. Below 10K, we observe an increase of susceptibility connected
with the polarization of the Eu sublattice by an effective exchange field of
the ordered Fe magnetic subsystem. In a magnetic field perpendicular to the
c axis, we have observed an increase of magnetization at T < 10K in the
applied magnetic field, which can be attributed to the appearance of the
magnetic moment induced by the magnetic field applied in the basal plane.
According to EPR measurements, the distance between the maximum and minimum
of derivative of absorption line of the Lorentz type is equal to 319Gs. The
anisotropy of g-factor and linewidth is due to the influence of crystalline
field of trigonal symmetry. The peculiarities of temperature dependence of
both intensity and linewidth are caused by the influence of excited states
of europium ion (Eu3+). It is supposed that the difference between the
g-factors from EPR and the magnetic measurements is caused by exchange
interaction between rare earth and Fe subsystems via anomalous Zeeman
effect.
Physics of Condensed Matter 04/2012; 78(3):291-298. · 1.53 Impact Factor
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M. T. Borowiec,
T. Zayarnyuk,
A. Pikul,
M. Gutowska,
M. C. Pujol,
M. Aguiló,
F. Díaz,
A. Szewczyk,
E. E. Zubov, V. P. Dyakonov,
M. Barański,
H. Szymczak
[show abstract]
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ABSTRACT: The specific heat of ARE(WO4)2, where A=K, Rb and RE=Y, Nd, Gd, Yb, and Lu single crystals, has been studied. The samples were grown using the Top Seeded
Solution Growth – Slow Cooling (TSSG-SC) method, and the resulting crystal structure data was tabulated. The specific heat
measurements as a function of temperature in the range from 0.35 to 385 K are presented. Above 2 K, the specific heat behavior
can be described by the phonon contribution while below 2 K, an anomalous increase in specific heat, attributed to the proximity
of magnetic phase transitions, was observed.
KeywordsCrystal growth-Crystal structure-Specific heat-Rare earth double tungstate-Debye temperature-Nuclear contribution of specific heat-Magnetic phase transition
Journal of Low Temperature Physics 04/2012; 160(3):119-130. · 1.19 Impact Factor
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ABSTRACT: The electron paramagnetic resonance (EPR) of Sm3+ ion in KY(WO4)2 single crystal was investigated at T = 4.2 K using an X-band spectrometer. The observed resonance absorption represents the complex superposition of three spectra corresponding to samarium isotopes with different nuclear moment. The EPR spectrum is characterised by a strong g -factor anisotropy. The temperature dependences of the g -factor were shown to be caused by strong spin–orbital and orbital–lattice coupling. The resonance lines become broader as temperature increases due to the short spin–lattice relaxation time. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 02/2009; 246(5):1105 - 1109. · 1.32 Impact Factor
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M T Borowiec, V P Dyakonov,
K Woźniak,
Ł Dobrzycki,
M Berkowski,
E E Zubov,
E Michalski,
A Szewczyk,
M U Gutowska,
T Zayarnyuk,
H Szymczak
[show abstract]
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ABSTRACT: Results of structural, magnetic and specific heat investigations of the potassium erbium double tungstate, KEr(WO4)2, are presented. Potassium erbium double-tungstate KEr(WO4)2 single crystals have been grown by the top-seeded solution growth method (TSSG) and modified Czochralski techniques. It crystallizes in the monoclinic crystal structure (C 2/c space group). The unit cell contains four formula units and is described by parameters a = 10.615(2) Å, b = 10.316(2) Å, c = 7.534(2) Å, β = 130.73(3)°. From the x-ray diffraction measurements the fractional atomic coordinates, displacement parameters and interatomic distances have been determined. The specific heat C(T) of the KEr(WO4)2 crystal has been measured over a temperature range of 0.6–300 K. The susceptibility has been studied at T = 0.25–4.0 K. The magnetic phase transition was observed at a temperature of 0.48 K. The magnetization has been measured in the temperature region from 4.2 to 60 K and in magnetic field up to 1.6 T. A strong anisotropy of magnetic properties was found. The temperature and field dependences of susceptibility and magnetization data were used for both elucidation of character of the magnetic ordering and calculation of the exchange and dipole–dipole interaction energies as well as for determination of the possible magnetic structure of KEr(WO4)2.
Journal of Physics Condensed Matter 01/2007; 19(5):056206. · 2.55 Impact Factor
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ABSTRACT: The isothermal, longitudal and transverse magnetostriction of rare earth double tungstates KDy(WO4)2, KHo(WO4)2 and RbNd(WO4)2 has been measured at low temperatures along the crystallographic axes in a magnetic field up to 12 T. The measurements have been performed by the strain gauge method on single crystals. For all three axes, we observed anomalies connected to the structural phase transitions induced by a collective Jahn–Teller effect or by strong external field at temperatures near a spontaneous structural phase transition of Jahn–Teller nature. It was shown that all the studied phase transitions are of first order. The magnetostriction measurements in rare earth double tungstates are important and interesting, since: (i) in these objects, there is a Jahn–Teller spontaneous structural transition at low temperatures; (ii) information on the behaviour of an elastic subsystem in these samples is necessary for understanding the mechanism of this transition under the influence of an external magnetic field applied along the crystallographic axes; (iii) it allows us to form a conclusion on the anisotropy of the studied phenomenon.
New Journal of Physics 08/2006; 8(8):124. · 4.18 Impact Factor
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ABSTRACT: Electron paramagnetic resonance (EPR) studies of Er3+ of single-crystal KY(WO4)2 have been carried out at X-band frequencies over a temperature range from 4.2 to 300 K. The main x- and z-axes of the g-tensor in the ac plane do not coincide with the crystallographic a-and c-axes, while the y- and b-axes are parallel. The EPR spectrum is characterized by a strong anisotropy of the g-factors (gz = 13.25 ± 0.05, gx = 0 ± 0.1, gy = 3.378 ± 0.005) and of the hyperfine interaction parameters (Az = −469 ± 3, Ax = 0 ± 3.5, Ay = −120.75 ± 0.8 in 10−4 cm−1). The temperature dependence of the g-factors is caused by an anharmonic part of the spin–phonon Hamiltonian as well as by a rotational contribution to this Hamiltonian. A spin–lattice relaxation is shown to result from two Orbach processes through the first and second excited levels of an electronic spectrum.
Journal of Physics Condensed Matter 07/2003; 15(29):5113. · 2.55 Impact Factor
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ABSTRACT: A theoretical substantiation is provided for realization of the spin structure in a weakly doped subsystem based on LaMnO3, which is observed in compounds with an excess of manganese, (La1−y
Cay)1− x
Mn1+x
O3, where y=0 and 0.3, x=0–0.4. It is proved experimentally that samples with x>0.1 exhibit an anomalous behavior of magnetization at T<45 K. The magnetization decreases in fields H<100 Oe and increases for H>200 Oe. It is assumed that this is associated with the emergence of a canted phase in clusters of manganese ions with difference
valences. A theoretical analysis indicates that a competition between double and superexchange interaction is in principle
possible in such clusters, since the charge carrier concentration in them is considerably lower than in the host matrix. It
is shown that the inclusion of quantum properties of spin leads to a considerable modification of the thermodynamic behavior
of a magnet with collectivized electrons. The results of analysis are compared with analogous results in the de Gennes classical
theory. The possibility of formation of a state with a canted magnetic sublattice in the weakly doped subsystem in the low-temperature
region is substantiated on the basis of calculations. An analysis of the thermodynamic behavior of the weakly doped subsystem
based of LaMnO3 taking into account quantum-mechanical properties of spin shows that relaxation phenomena determined, to a considerable extent,
by the relation of parameters of intra-and interplanar indirect exchange, as well as the electron transport energy, can take
place in the region of phase transition to the canted state. The microscopic parameters of interactions are estimated quantitatively.
The results of calculations are in qualitative agreement with experimental data.
Journal of Experimental and Theoretical Physics 11/2002; 95(6):1044-1055. · 1.03 Impact Factor
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ABSTRACT: Magnetic phase transition in the CsDyW2O8 magnet has been studied by means of low temperature specific heat C
(
T
) measurements. The magnetic ordering temperature of the Dy3+ sublattice was established to be 1.34 K. The experimental results indicate on the antiferromagnetic character of interactions
between Dy3+ ions. The behavior of the C
(
T
) dependencies above and below T
N
is discussed in frames of different theoretical models. The measurements data on temperature and field dependencies of magnetization
are used to calculate the exchange and dipole-dipole interactions energy and to determine the possible magnetic structure
of the ground state.
Physics of Condensed Matter 08/2002; 29(1):9-14. · 1.53 Impact Factor
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ABSTRACT: The pressure controlled oxygen reordering processes in REBa
2
Cu
3
O
6+x
(RE=Y,Nd,La) causing the continous charge transfer between the CuO
x
and CuO
2
planes were investigated. The charge transfer results in the time evolution of superconductivity. A strong acceleration of ordering and disordering processes was found when the RE-ion size increases from Y to La. Pressure induced semiconductor-superconductor transition in LaBa
2
Cu
3
O
6+x
resulted from the oxygen ordering is reported for the first time.
Journal of Low Temperature Physics 10/1999; 117(3):909-913. · 1.19 Impact Factor
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ABSTRACT: The specific heat of has been measured over the wide temperature range from 3.5 K to 200 K. Only one anomaly, indicating the phase transition driven by the cooperative Jahn-Teller effect, has been found, at . The phonon specific heat has been estimated and subtracted from the heat capacity measured. The Schottky anomaly originating from the population of the lowest two doublets of the dysprosium ions, and the -anomaly connected with the Jahn-Teller phase transition have been described theoretically using the molecular-field approximation. Satisfactory agreement between experimental points and theoretical dependences calculated using the material parameters known from the literature was obtained.
Journal of Physics Condensed Matter 12/1998; 10(47):10539. · 2.55 Impact Factor
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ABSTRACT: The specific heat C(T) of the monoclinic RbDy(WO
4
)
2
crystal has been studied at very low temperatures 0.2T1.9 K and in magnetic fields 0H0.38 T. The Neel temperature was shown to be equal to TN = 0.818 0.005 K. The experimental value of the effective exchange parameter was obtained to be equal to J/k = – 0.798 K. The C T) dependence below Neel temperature 0.5TN0.99TN
) is well described by 2D Ising model, whereas in the temperature region close above TN
(1.01 TN2TN) it can be described by neither 2D, nor 3D Ising model. The experimental and theoretical H-TN
diagrams for field
H a
are in a reasonable agreement for simple quadratic lattice.
Journal of Low Temperature Physics 02/1998; 110(5):1003-1011. · 1.19 Impact Factor
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ABSTRACT: The magnetic phase transition in the KDy(WO4)2 single crystal has been first studied using the temperature dependence of the specific heat in a magnetic field. The ordering temperature of the Dy3+ sublattice was established to be TN = 0.60 ± 0.02 K. The specific heat data are indicative of the antiferromagnetic character of Dy3+ ions' interactions in the ac plane. The value of the effective interaction parameter was estimated. A part of the entropy is shown to be released at and above the transition temperature only. The temperature dependence of the specific heat above and below TN is discussed in the frameworks of the theoretical 2D and 3D Ising and XY models.
Physics Letters A. 243:85-90.
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M.T. Borowiec,
T. Zayarnyuk,
M.C. Pujol,
M. Aguiló,
F. Díaz,
E.E. Zubov,
A.D. Prokhorov,
M. Berkowski,
W. Domuchowski,
A. Wisniewski,
R. Puzniak,
J. Pietosa, V.P. Dyakonov,
M. Baranski,
H. Szymczak
[show abstract]
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ABSTRACT: Magnetic properties of KGd(WO4)2, KYb(WO4)2 and KTm(WO4)2 single crystals have been studied. Temperature and field dependences of the magnetization along the main magnetic axes and angular dependence of the magnetization in the planes settled on the magnetic axes were recorded in the temperature range from 2 up to 100 K and in magnetic field up to 9 T. Paramagnetic Curie temperatures, g-factors and exchange interaction parameters were determined. Different theoretical models were used to describe magnetic properties of KGd(WO4)2 and KYb(WO4)2 crystals.
Physica B Condensed Matter 405(23):4886-4891. · 1.06 Impact Factor
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ABSTRACT: Pressure-controlled oxygen reordering responsible for the appearance of time-dependent superconductivity in originally nonsuperconducting underdoped RBa2Cu3Ox (R=Y, Nd, La) was studied by magnetization and x-ray diffraction measurements. The rate of the reordering process, determined by the activation energy Ea of oxygen hopping in the basal plane, depends strongly on both pressure and R-ion size. The activation energy was found to decrease linearly with the increase of the unit-cell volume, at a rate of -0.018 eV/Å3. This Ea dependence on volume for strongly underdoped compounds is shown for both pressure and R-ion substitution. This relation allows understanding the significant differences in time-dependent properties observed among compounds of RBa2Cu3Ox series.
Phys. Rev. B. 66(1).
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The European Physical Journal B - Condensed Matter and Complex Systems. 78(3):291-298.
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ABSTRACT: The electron paramagnetic resonance (EPR) of Yb 3+ ions in a KY(WO 4 ) 2 single crystal was investigated at T=4.2 K and fixed frequency of 9.38 GHz. The resonance absorption observed on the lowest Kramers doublet represents the complex superposition of three spectra, corresponding to the ytterbium isotopes with different nuclear moments. The EPR spectrum is characterized by a strong anisotropy of the g-factors. The temperature dependence of the g-factors is shown to be caused by the strong spin-orbital and orbital-lattice coupling. The resonance lines broaden with increasing temperature due to the short spin-lattice relaxation times. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007
The European Physical Journal B - Condensed Matter and Complex Systems. 55(4):389-395.
