Search

X-ray diffraction and magnetic measurements of polycrystalline and nanosize TbMnO₃ manganites have been performed. All the compounds studied crystallize in the orthorhombic crystal structure (space group Pnma) at room temperature. The nanosize manganites were synthesized with a sol-gel method at different (800 and 900°C) temperatures. The average size of synthesized nanoparticles (from 45 to 70 nm) was estimated by using the x-ray diffraction and low-temperature adsorption of argon methods. An information on the evolution of properties of TbMnO₃ with changing grain size, temperature and magnetic field was obtained. The crystal structure parameters of nanospecimens change slightly with changing the nanoparticle size. The peculiarities of magnetic ordering in polycrystalline and nanosize TbMnO₃ were compared. Magnetization and the Nèel temperature corresponding to antiferromagnetic ordering of the Tb³⁺ sublattice decrease as the particle size is reduced. The inverse magnetic susceptibility of the nanoparticle samples deviates from the Curie–Weiss law below 50 K, that is connected with the magnetic ordering of the Mn³⁺ moments. Specific heat of the nanosize samples exhibits anomalies related to the magnetic ordering of the Tb³⁺ and Mn³⁺ sublattices.

Temperature dependence of dc/ac magnetization and electron paramagnetic resonance (EPR) spectra of Pb2FeV3O11 iron lead vanadate has been investigated. The dc magnetic measurements have shown the presence of antiferromagnetic interactions with Curie-Weiss temperature, T CW = -15.2 K, in the high temperatures range while the field cooled (FC) magnetization revealed a maximum at TN = 2.5 K which coincides with a long range magnetic ordering. Temperature dependence of χ′ has shown a maximum at the same temperature. EPR spectrum of Pb2FeV 3O11 at room temperature is dominated by nearly symmetrical, very intense and broad resonance line centered at geff ∼ 2.0 that could be attributed to the correlated system of iron ions. The temperature dependence of magnetic resonance parameters (amplitude, g-factor, linewidth, integrated intensity) has been determined in the 4-300 K range and it suggests the existence of short range correlated spin system up to high temperatures. The temperature dependence of the amplitude of the resonance line has shown a pronounced maximum at 12.5 K that indicates on the existence of two subsystems of weakly and strongly coupled iron pairs. Comparison of dc magnetic susceptibility and EPR integrated intensity points to the presence of correlated spin agglomerates that play an important role in determination of the magnetic response of Pb2FeV3O11. © 2011 Elsevier B.V.

We present a detailed study of layered semiconductor InSe doped with Mn. Xray and neutron diffraction analyses of (In,Mn)Se single crystals show the presence of a main phase as In₁−xMnxSe solid solution, the second antiferromagnetic MnSe phase, and traces of In₄ Se₃ Magnetic measurements reveal ferromagnetic behavior of (In,Mn)Se with the Curie temperature about 800 K. The ferromagnetic cluster model and exchange interaction via 2D electron gas, as the reasons of spontaneous magnetization, are discussed. The dramatic transformation of (In,Mn)Se electron spin resonance (ESR) spectra as a function of temperature is revealed. At the magnetic field perpendicular to crystallographic c axis, a low-field line within the temperature range 70 down to 4.7 K is observed. It shifts to smaller magnetic fields with temperature decrease. Neutron diffraction studies reveal the strong rise for one of the reflection peaks with temperature decrease in the same temperature region where ESR spectra transformation occurs. This peak corresponds to double MnSe interplanar distance in the [111] direction what is a period of its magnetic lattice. Magnetic structure of (In,Mn)Se single crystal is discussed.

Исследовано влияние равноканального многоуглового прессования в комбинации с гидроэкструзией и волочением, а также заключительной термообработкой на плотность критического тока, силу пиннинга и температуру сверхпроводящего перехода биметаллического провода на основе сплава Nb + 60 ат.% Ti. Досліджено вплив рівноканального пресування у комбінації з гідроекструзією та волочінням, а також заключною термообробкою на щільність критичного струму, силу пінінгу та температуру надпровідного переходу біметалічного проводу на основі сплаву Nb + 60 ат.% Ti. The effect of the equal-channel multiple-angle pressing combined with hydroextrusion and drawing followed by heat treatment on the critical current density, pinning force and superconducting transition temperature of the bimetallic wire based on alloy Nb + 60 at.% Ті has been investigated.

Проведены измерения температурных M(T) и полевых M(H) зависимостей намагниченности в монокристалле TbBaCo₄O₇ для двух направлений магнитного поля H || c и H ⊥ c. В случае H || c при низких температурах обнаружен индуцированный магнитным полем необратимый переход, сопровождаемый скачками намагниченности на зависимостях M(H). Показано, что величина поля перехода зависит от скорости введения внешнего магнитного поля. Проведено виміри температурних M(T) та польових M(H) залежностей намагніченості у монокристалі TbBaCo₄O₇ для двох напрямків магнітного поля H || c та H ⊥ c. У випадку H || c при низьких температурах виявлено індукований магнітним полем необоротний перехід, який супроводжується скачками намагніченості на залежностях M(H). Показано, що величина поля переходу залежить від швидкості введення зовнішнього магнітного поля. The temperature and field dependences of magnetization, M(T) and M(H) of the single crystal TbBaCo₄O₇ were measured for two directions of magnetic field H || c and H ⊥ c. A magnetic fieldinduced irreversible transition was observed at low temperatures for H || c. The transition is accompanied by a magnetization jump in the M(H) dependences. It is shown that the transition field depends on magnetic field sweep rate.

Magnetic interactions in a site-disordered multicomponent vanadate Mn3Fe4(VO4)6 are studied using DC magnetization and multifrequency Electron Paramagnetic Resonance (EPR). The static magnetic susceptibility χ shows antiferromagnetic interactions between Fe3+ and Mn2+ spins with a Curie-Weiss temperature Θ = -165(5) K. EPR measurements indicate a strong dependence of χ on the frequency and temperature. The EPR spectra due to iron and manganese ions are observed in the X-band. It is mostly manganese ions that are observed at 80 GHz while two kinds of magnetic centers are identified at frequencies above 160 GHz. The observed shifts of the resonance lines for Fe3+ ions at low frequencies differ from those at high frequencies. The observed features may be due to different magnetic sublattices which modify the magnetic ground state, while competing magnetic interactions may lead to magnetic frustration. It appears that the very high magnetic fields employed in our high-frequency EPR measurements may affect the spin-flop transitions anticipated below Neel temperature TN. © 2009 Elsevier B.V. All rights reserved.

The magnetic properties of γ-Fe 2O 3 nanoparticles embedded in a thermoplastic elastomer poly(ether-ester) copolymer by the in situ polycondensation reaction process have been investigated by means of magnetization and ferromagnetic resonance (FMR) measurements at low filler concentrations of 0.1 and 0.3 wt% with the magnetic additive introduced in the polymer matrix in powder and solution form. The magnetic behavior of the magnetopolymeric nanocomposites indicates significant interparticle interaction effects that depend mainly on the dispersion state of the magnetic nanoparticles as well as their concentration, consistent with the variation of the particle microstructure characterized by magnetic aggregates in the nanometer and micron scale for the solution and powder dispersions, respectively. The magnetization and FMR results at different filler concentrations and dispersions show a close correspondence to the relaxation processes of the copolymer, implying the coupling of polymeric and magnetic properties. Copyright © 2008 American Scientific Publishers All rights reserved.

Temperature dependence of dc magnetization and ferromagnetic resonance (FMR) of two samples containing γ-Fe2O3 (maghemite) magnetic nanoparticles dispersed at low concentration (0.1 and 0.3 wt%) in a nanocomposite based on a poly(ether-ester) multiblock copolymer (PTT-block-PTMO) matrix was investigated. The polymer filler was in a powder form consisting of small-sized magnetic nanoparticles arranged in agglomerates 2-3 μm long and 100 nm thick. The studied samples were characterized by SEM spectroscopy. The SEM showed that the concentration of magnetic nanoparticles was homogenous in both samples The temperature dependence of the dc magnetization revealed that the blocking was about 100 K and the ZFC (zero-field cooling) mode at low magnetic fields uncovered the presence of magnetic interactions between magnetic nanoparticles depending on the properties of the matrix. FMR measurements were carried out in the temperature range 4.2-300 K. An intense resonance absorption line attributed to γ-Fe2O3 nanoparticles was recorded with a slightly asymmetric lineshape. At room temperature the resonance line was centered at Hr = 3241(2) and 3253(2) G, with linewidths of ΔH = 1069(1) and 1070(1) G for samples with concentrations of 0.1 and 0.3 wt%, respectively. All FMR parameters showed an anomalous behavior at matrix critical temperatures. It was shown that the difference in concentration of magnetic nanoparticles could be responsible for the observed differences in the thermal behavior of the FMR spectra. © 2008 Elsevier B.V. All rights reserved.

The magnetic and magnetoresonance properties of a new single-crystal compound Ni₅(TeO₃)₄Cl₂ are studied. The measurements of the magnetization and magnetic susceptibility of the crystal in a wide temperature range (5–300 K) made it possible to conclude that Ni₅(TeO₃)₄Cl₂ is a quasi-two-dimensional antiferromagnet with the easy magnetization axis a* directed perpendicular crystallographic plane bc and a magnetic ordering temperature TN≈21 K. The resonance measurements at 4.2 K in wide range of frequencies (25–105 GHz) and magnetic field (up to 200 kOe) permitted us to obtain the frequency–field dependence of AFMR spectrum for a field applied along the easy magnetization axis a*. It is shown that the magnetic field directed along the antiferromagnetism axis (H||a*) induces the magnetic phase transition of a spin-flop type which is found to be Hsf≈120 kOe. The magnetic resonance experimental data are described qualitatively in model of the biaxial antiferromagnet.

The magnetic properties of the site ordered multicomponent vanadate Mg3Fe4(VO4)(6) are studied using dc magnetization and electron paramagnetic resonance (EPR) measurements. The static susceptibility shows antiferromagnetic interactions between Fe3+ spins with a Curie-Weiss temperature Theta=-111(1) K, while a transition to a spin-glass-like state is observed at T approximate to 8.5 K, indicating appreciable spin frustration. EPR measurements corroborate the presence of antiferromagnetically coupled Fe3+ spins from high temperatures, while a distinct change in the temperature variation of the EPR parameters is observed at T < 80 K, complying with the mean-field energy scale provided by the Curie-Weiss temperature of the system. The resulting magnetic inhomogeneity that persists despite the absence of cation disorder between magnetic and diamagnetic metal ions is attributed to the presence of small amounts of oxygen deficiency that modifies the connectivity and superexchange coupling between Fe3+ spins and leads to a disordered magnetic ground state. (c) 2007 American Institute of Physics.

The magnetic properties of gamma-Fe2O3 ferrimagnetic nanoparticles embedded in a multiblock poly(ether-ester) copolymer have been investigated by static magnetization and ferromagnetic resonance (FMR) measurements at two different dispersion states. Significant variation of the magnetic response is identified below T approximate to 120 K, most pronounced in the marked resonance field shift of the FMR spectra, independently of the dispersion state of the nanocomposites. This behavior correlates favorably with the dynamic relaxation of the copolymer, indicating a matrix freezing effect that is attributed to the magnetoelastic coupling of the oxide nanoparticles with the surrounding polymer. At low temperatures, the dc magnetization and FMR measurements vary considerably for the two nanocomposites, indicating essential differences in their ground state, related to the different morphology of the samples and the concomitant variation of interparticle interactions. (C) 2006 American Institute of Physics.

Определена температурная зависимость поля коэрцитивности Hc многослойной пленки [Gd75Å/Si5Å/Co30Å/Si5Å]₂₀ с ферримагнитным упорядочением магнитных моментов слоев кобальта и гадолиния. Максимальное значение Hc наблюдается при температуре около 118 К, соответствующей точке компенсации пленки. Установлено, что на всем исследуемом температурном интервале изменение поля коэрцитивности вызвано изменением спонтанной намагниченности The temperature dependence of coercive field Hc of the multilayered [Gd75Å/Si5Å/Co30Å/Si5Å]₂₀ film with a ferrimagnetic ordering of the magnetic moments of cobalt and gadolinium layers has been determined. The maximal value of Hc was observed at a temperature about the compensation point of 118 K. A strong correlation between the changes in coercive field and spontaneous magnetization in the studying temperature range is established. Визначено температурну залежність поля коерцитивності Hc багатошарової плівки [Gd75Å/Si5Å/Co30Å/Si5Å]₂₀ з феримагнітним упорядкуванням магнітних моментів шарів кобальту і гадолінію. Максимальне значення Hc спостерігається при температурі близько 118 К, що відповідає точці компенсації плівки. Установлено, що на всьому дослідженому температурному інтервалі зміна поля коерцитивності викликана зміною спонтанної намагніченості.

International audience; The crystal structure, magnetization and electrical transport depending on the temperature and magnetic field for the doped stoichiometric La 1-x 3+Srx 2+Mn1-x 3+Mnx 4+O3 2- as well as anion-deficient La1-x 3+Srx 2+Mn 3+O3-x/2 2- (0 ≤ x ≤ 0.30) ortomanganite systems have been experimentally studied. It is established that the stochiometric samples in the region of the 0 ≤ x ≤ 0.125 are an O'-orthorhombic perovskites whereas in the 0.175 ≤ x ≤ 0.30 - a rhombohedric. For the anion-deficient system the symmetry type of the unit cell is similar to the stoichiometric one. As a doping level increases the samples in the ground state undergo a number of the magnetic transitions. It is assumed that the samples with the large amount of oxygen vacancies are a cluster spin glasses (0.175 < x ≤ 0.30) and temperature of the magnetic moment freezing is ∼40 K. All the anion-deficient samples are semiconductors and show considerable magnetoresistance over a wide temperature range with a peak for the x = 0.175 only. Concentration dependences of the spontaneous magnetization and magnetic ordering temperature for the anion-deficient La1-x 3+Srx 2+Mn3+O3-x/2 2- system have been established by the magnetic measurements and compared with those for the stoichiometric La1-x 3+Sr x 2+Mn1-x 3+Mnx 4+O3 2- one. The magnetic propeprties of the anion-deficient samples may be interpreted on the base of the superexchange interaction and phase separation (chemical disorder) models.

Исследовано влияние светового облучения на магнитные и транспортные свойства эпитаксиальных тонких пленок манганита Pr₀,₆La₀,₁Ca₀,₃MnO₃. Обнаружено, что облучение пленок светом He–Ne лазера приводит к увеличению их намагниченности и уменьшению электрического сопротивления, стимулируя фазовый переход антиферромагнитный диэлектрик—ферромагнитный металл, наблюдаемый в этом кристалле в магнитном поле при низких температурах. Показано, что поле фазового перехода заметно уменьшается после облучения пленок светом. Сделан вывод о том, что световое облучение вызывает образование и рост ферромагнитных металлических кластеров внутри антиферромагнитной диэлектрической фазы. Механизм воздействия света на магнитное и электрическое состояния манганита Pr₀,₆La₀,₁Ca₀,₃MnO₃ может быть связан с фотоиндуцированным переносом электронов с ионов Mn³⁺ на ионы Mn⁴⁺, что приводит к плавлению зарядового упорядочения, имеющего место в исследуемом манганите в антиферромагнитном диэлектрическом состоянии, и вызывает переход кристалла в ферромагнитную металлическую фазу. Вивчено вплив світлового опромінення на магнітні та транспортні властивості епітаксіальних тонких плівок манганіту Pr₀,₆La₀,₁Ca₀,₃MnO₃. Виявлено, що опромінення плівок світлом He–Ne лазера приводить до зростання їх намагніченості та зменшення електричного опору, стимулюючи фазовий перехід антиферомагнітний діелектрик—феромагнітний метал, що спостерігається у цьому кристалі в магнітному полі при низьких температурах. Показано, що поле фазового переходу помітно зменшується після опромінення плівок світлом. Зроблено висновок, що світлове опром інення приводить до виникнення та розростання феромагнітних металевих кластерів всередині антиферомагнiтної діелектричної фази. Механізм впливу світла на магнітний та електричний стани манганіту Pr₀,₆La₀,₁Ca₀,₃MnO₃може бути пов’язаний з фотоіндукованим переносом електронів з іонів Mn³⁺ на іони Mn⁴⁺, що призводить до плавлення зарядового впорядкування, яке має місце в дослідженому манганіті в антиферомагнітному діелектричному стані, та викликає перехід кристалу до феромагнітної металевої фази. The effect of light illumination on the magnetic and transport properties of epitaxial thin films of manganite Pr₀,₆La₀,₁Ca₀,₃MnO₃ was studied. It has been found that the illumination of films with He–Ne laser light in the external magnetic field increases magnetization and decreases electric resistance. The antiferromagnetic dielectric—ferromagnetic metal phase transition that is observed in this crystal in the magnetic field at low temperatures is stimulated by light. It has been found that the phase transition field decreases noticeably after light illumination. It can be concluded that light illumination induces the formation and increase of ferromagnetic conductor clusters within the antiferromagnetic dielectric phase. The mechanism of the effect of light on the magnetic and transport properties of Pr₀,₆La₀,₁Ca₀,₃MnO₃ can be related to the photoinduced electron transfer from Mn³⁺ to Mn⁴⁺ ions. This process stimulates the melting of the charge ordering that exists in this manganite in the dielectric state as well as the transition of the crystal to the ferromagnetic metal phase.

The magnetic properties of the Zr2FeV3O11 vanadate, characterized by a disordered distribution of diamagnetic Zn 2+ and high-spin Fe3+ ions, are studied using magnetization and electron paramagnetic resonance (EPR) measurements. The dc susceptibility reveals antiferromagnetic interactions between Fe3 +spins with a Curie-Weiss temperature Θ = -58(1) K, followed by a transition to a frozen, spin-glass-like state at low temperature T f ≈ 2.55 K, indicating an inhomogeneous magnetic ground state. The temperature variation of the EPR parameters confirms the antiferromagnetic coupling of Fe3+ spins at high temperatures, while a distinct divergence is observed at T ≈ 55 K. This behavior is attributed to the inherent magnetic inhomogeneity of the system due to antiferromagnetic spin clusters.

We have measured the temperature dependence of gap features revealed by Andreev reflection (Ds) and by tunneling (D) in the ab-plane of optimally and slightly overdoped microcrystals of (BiPb)₂Sr₂Ca₂Cu₃O₁₀₊δ (Bi2223) with critical temperature Tc = 110-115 K, and Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) with Tc = 80-84 K. The tunneling conductance of a Bi2223-insulator-Bi2223 junction shows peaks at the 2D gap voltage, as well as dips and broad humps at other voltages. In Bi2223, similarly to the well-known Bi2212 spectra, the energies corresponding to 2D, to the dip, and to the hump structure are in the ratio 2:3:4. This confirms that the dip and hump features are generic to the high-temperature superconductors, irrespective of the number of CuO₂ layers or the BiO superstructure. On the other hand, in both compounds the D(T) and Ds(T) dependences are completely different, and we conclude that the two entities are of different natures.

La1-xMnO3 films grown by metal organic chemical vapor deposition technique on r-plane cut Al2O3 substrates were investigated. The change of the optical response over the La1-xMnO3/Al2O3 sample surface was investigated along with the temperature dependence of magnetization. The mostly pronounced difference in the spectra of dielectric function occurred in the region of the d-d transitions of Mn-ions. The changes in the optical spectra and magnetic properties were correlated to the structural features of thin film.

Influence of water molecule coordination on the magnetic properties of polyamine copper dinitrate complexes was studied. It was found that the magnetic coupling between Cu2+ ions strongly depends on the presence of water molecules in the crystal structure. Electron paramagnetic resonance (EPR) measurements showed considerable temperature dependence of the Lande′ splitting factors and resonance linewidths for both complexes at low temperatures.

Представлены результаты магнитных и магнитооптических исследований магнитных конфигураций в трехслойной пленке Fe(30Ǻ)/Si(14Ǻ)/Fe(30Ǻ), в которой наблюдается ферромагнитный и биквадратный обмен между слоями железа, а также кубическая и одноосная анизотропия. Исследования проводились при температурах 300 и 10 К. Обнаружено, что в изученной системе в отсутствие магнитного поля наблюдается неколлинеарная магнитная структура, которая меняет свой вид с температурой. Проведен расчет устойчивых неколлинеарных конфигураций на основе модели, в которой предполагалось изменение с температурой как констант обменного взаимодействия, так и констант кубической и одноосной анизотропии в слоях железа. В результате сравнительного анализа экспериментальных данных и расчета определены величины углов, характеризующих направление намагниченности в слоях железа в устойчивых неколлинеарных конфигурациях. Показано, что в исследованной системе с температурой меняется как угол между направлениями намагниченности в двух слоях железа, так и направление легкой оси всей системы. Представлено результати магнітних і магнітооптичних досліджень магнітних конфігурацій у трьохшаровій плівці Fe(30Ǻ)/Si(14Ǻ)/Fe(30Ǻ), в якій спостерігається феромагнітний та біквадратний обмін між шарами заліза, а також кубічна та одноосна анізотропія. Дослідження проведено при температурах 300 та 10 К. Виявлено, що у системі, що вивчалася, у відсутності магнітного поля існує неколінеарна магнітна структура, яка змінює свій вигляд з температурою. Проведено розрахунок стійких неколінеарних конфігурацій на базі моделі, в якій припускалось зміну з температурою як констант обмінної взаємодії, так і констант кубічної та одноосної анізотропії у шарах заліза. У результаті порівняльного аналізу експериментальних даних та розрахунку визначено величини кутів, які характеризують напрямки намагніченості у шарах заліза у стійких неколінеарних конфігураціях. Показано, що у системі, що досліджувалася, з температурою змінюється як кут між напрямками намагніченості у двох шарах заліза, так i напрямок легкої осі всієї системи. Results are presented from magnetic and magnetooptical studies of the magnetic configurations in a three-layer film Fe(30 Å)/Si(14 Å)/Fe(30 Å) in which ferromagnetic and biquadratic exchange between iron layers is observed and which also possesses cubic and uniaxial anisotropy. These studies were done at temperatures of 300 and 10 K. It was found that in the absence of magnetic field a noncollinear magnetic structure, the form of which changes with temperature, is observed in this system. A calculation of the stable noncollinear configurations is done on the basis of a model in which it is assumed that both the exchange interaction constant and the cubic and uniaxial anisotropy constants in the iron layer change with temperature. The values of the angles characterizing the magnetization direction in the iron layers in the stable noncollinear configurations are determined on the basis of a comparative analysis of the experimental data and the results of the calculation. It is shown that both the angle between the magnetization directions in the two iron layers and the direction of the easy axis of the system as a whole change with temperature.

Transmission electron microscopy and X-ray diffraction proved chain/ladder incommensurate single crystal structure of investigated samples. The incommensurate ratio was determined from the X-ray and electron diffraction being equal to 0.704. Diffuse scattering intensities localised on the planes perpendicular to the c*-axis and passing through the spots originating from the periodicity of chain sublattice were detected. High-angle grain boundary or twinning formed by rotation of 33.3 degrees around [100] direction was observed. High-resolution electron microscopy images revealed the stacking faults in ac planes.

Two binuclear copper(II) complexes with macrocyclic Schiff bases Cu2LI(CH3COO)2·5H2O (complex I) and Cu2LII(CH3COO)2·2H2O (complex II) were synthesized and then characterized by IR, UV, and thermogravimetric analysis (TGA) measurements. TGA was used to investigate the desolvation of lattice water molecules. IR spectra demonstrated the formation of the cyclic compound and together with chemical elemental analysis were used to propose the structure of the complexes. The UV spectra of both complexes are typical for binuclear copper(II) complexes with Robson-type ligands. Variable-temperature magnetic susceptibility measurements corroborated by EPR and low-temperature isothermal magnetization data confirmed the formation of copper dimers with antiferromagnetic exchange coupling constants of -400 and -1250 cm-1 for complexes I and II, respectively, residing outside the usual range for the phenoxide bridged Cu(II) complexes. This implies the possibility that additional superexchange paths through the macrocyclic ligand may affect the intradimer exchange interaction as well as the phenoxide oxygen bridges.

A polycrystalline sample of Ce₃Pd₂₀Ge₆ is investigated using a dc SQUID magnetometer. A noticeable difference between ZFC and FC magnetic susceptibility is found below ≈60 K. The temperature dependence of the magnetic susceptibility demonstrates an anomaly near approximately 2.8K below which a remanent magnetic moment exists. Two characteristic temperatures detected support the assumption that there are different cerium magnetic subsystems in Ce₃Pd₂₀X₆ (X= Ge,Si) compounds. Unusual magnetic behavior observed in Ce₃Pd₂₀Ge₆ is discussed within the framework of the "molecular magnetism" model which predicts a frustration of exchange interactions.

Magnetic anisotropy of layered superconducting Bi2Sr2CaCu2O x single crystal was investigated by the torque metlod in the reversible regime. The torque was analyzed in the model taking into account 2D layered structure. Considered model gives the better fit to the data wlen the magnetic fieJd is applied near (a, b) plane. Obtained results establish to 6 x 10 3 value of the superconducting effective mass anisotropy coefficient ε.