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This paper presents results on the synthesis of multicomponent $$\textrm{Sm}_{0.2}(\textrm{Y},\textrm{Tb})_{0.8}\textrm{Fe}_{2}$$ alloys and the study of their magnetostriction properties. In this system, it is possible to control competing exchange interactions by varying the concentrations of components, the temperature, and the external magnetic field and to observe a variety of unique phenomena, such as magnetization and magnetostriction compensation. Using X-ray diffraction analysis, it has been established that these alloys have a cubic crystal structure of the C15 Laves phase. Longitudinal and transversal magnetostrictions were studied within a temperature range from 80 to 300 K in magnetic fields of up to 12 kOe. The bulk and anisotropic magnetostrictions were calculated from experimental values. The sign inversion of bulk magnetostriction in Sm $${}_{0.2}$$ Y $${}_{0.8}$$ Fe $${}_{2}$$ was revealed at $$T=150$$ K. It has been shown that the bulk magnetostriction of some studied alloys is almost invariable and close to zero within a broad temperature range of 150–300 K. The results are discussed within the model of a three-sublattice magnet with competing exchange interactions.

Influence of hydrogenation on the microstructural parameters, surface topology, and temperatures of magnetic phase transitions in Dy2Fe10Al7 was studied. Thermomagnetic properties in the obtained hydride Dy2Fe10Al7H3.2 were also investigated. Hydrogenation was found not to change the Curie point of the compound Dy2Fe10Al7, but at the same time it affects remarkably the temperature of the magnetic compensation transition. The coercive force increases upon hydrogenation, and thus the magnetocrystalline anisotropy can be concluded to increase due to changes in the local environment of the dysprosium ion caused by insertion of hydrogen atoms into the crystal lattice. The relative volume change ΔV/V of the unit cell of the hydride Dy2Fe10Al7H3.2 was shown to be 3%. The investigation of the peculiarities of the structural state allowed concluding that hydrogenation causes significant modification of the microstructure, which in turn changes the physical and functional properties of the hydrogenated materials.

The magnetostructural phase transition in Mn(As,P) compounds was studied by a combination of X-ray diffraction on single crystals and by the magnetisation measurements. The mentioned transition is accompanied by anisotropic deformation of the crystal lattice, magnetisation hopping and heat evolving due to a large magnetocaloric effect (MCE). It is shown that this transition is a transformation from the hexagonal ferromagnetic to the orthorhombic paramagnetic phase at heating above the Curie temperature (TC). The values of the magnetic and lattice entropy changes at phase transition are obtained and the adiabatic temperature change is estimated in the frame of Clapeyron-Clausius relations. It is found that the MCE in the magnetic field 140 kOe reaches the value of 13.5 K. It is shown that a superparamagnetic structure (as a conglomerate of microscale areas) is formed above Curie temperature in zero magnetic field. On the other hand at the temperatures above the TC the ferromagnetic state is induced by magnetic fields exceeding the certain critical value Hcr while the above-mentioned superparamagnetic state is destroyed by the same magnetic fields. The magnetic properties of the bulk Mn(As,P) and the polymeric composite based on Mn(As,P) compound are compared.

The paper presents the results of studying the alloy magnetization of the multicomponent system (Tb1−xYx)0.8Sm0.2Fe2. The substitution parameter in this system takes the following values: x = 0, 0.2, 0.4, 0.6, 0.8, 1. In the system, the atoms of magnetic terbium were replaced by atoms of weakly magnetic samarium and nonmagnetic yttrium. X-ray diffraction analysis determined the structure and lattice constant for all compositions. Phase analysis was carried out. It is known that by varying the concentration of components, temperature, and external fields, one can successfully influence the magnitude of exchange interactions leading to one or another type of magnetic ordering in the rare-earth intermetallic metals. Therefore, the main goal in this work was to investigate the possibility of observing the magnetic phase transition – ferrimagnetism – ferromagnetism - in the alloys of the system from the curves of the field dependence of magnetization in strong fields up to 60 T. The studies were carried out at the liquid helium boiling point. The main magnetic characteristics of the alloys of this system were determined, such as saturation magnetization σs, magnetic moment per formula unit μ and magnetic moment μFe on iron atoms. Their dependences on the concentration of yttrium were established. The possible values of the magnetic moment per formula unit in the case of ferromagnetic ordering of these alloys were calculated theoretically. It was concluded that these fields are insufficient to observe the ferrimagnetism – ferromagnetism phase transition.

The equiatomic intermetallic alloy MnZnSb with a tetragonal Cu2Sb-type crystal structure (space group P4/nmm) was melted in the resistance furnace in the evacuated quartz ampoule. The adiabatic temperature change ( Δ T ad ) and the isothermal variation of the magnetic entropy ( Δ S M ) of the MnZnSb compound near to the magnetic phase transition were studied. The Δ T ad in a magnetic field up to 1.25 T was studied by the direct method. It was found that temperature dependencies of both Δ T ad and Δ S M show a sharp peak near room temperature with a maximum at Curie temperature T C = 317 K. It was shown that there is no temperature hysteresis of the Δ T ad in MnZnSb, and the maximum of Δ T ad when the compound is heated or cooled is detected at the same temperature. The estimated value of Δ T ad in a field of 14 T is 4.5 K. It was shown that near the Curie temperature, the field dependence of the maximum of magnetic entropy change is adequately described by the thermodynamic Landau theory for magnetic second-order phase transitions.

The influence of partial substitution of Co by Al atoms on the magnetocaloric and magnetostrictive properties of the multicomponent Tb-Dy-Gd-Co compounds with a Laves phase structure was investigated. The samples were obtained by arc melting using of high-purity rare-earth metals. The crystal structure of Tb 0.2 Dy 0.8 - x Gd x Co 2 - y Al y (x = 0.3, 0.4, and 0.5; y = 0 and 0.1) compounds was monitored by powder X-ray diffraction. The magnetostriction and the magnetocaloric effect in external magnetic field up to 12 and 18 kOe, respectively, were studied in wide temperature range. The Curie temperature of Al-content compounds increases by an average of 20 K, while the magnitudes of the magnetocaloric effect and the magnetostriction slightly decrease.

Magnetic properties of hydrides of the intermetallic compound Nd 2 Fe 14 BH x are investigated in the temperature range covering the Curie temperatures ( T C ) of the compounds (up to 670 K). The temperature dependencies of magnetization are measured under continuous control of hydrogen content in the investigated samples. The dependencies of Curie and spin-reorientation transition ( T SR ) temperatures on the hydrogen concentration are studied in detail. The dependence of hydrogen concentration on pressure at a constant temperature (near T C ) and on the temperature at various pressures are obtained. We attempted to estimate the contributions of the unit cell volume increase upon hydrogenation and the electronic structure change in the variation of T C of the hydrogenated Nd 2 Fe 14 B .

The structural and magnetic properties of Sm0.2Y0.8Fe2 intermetallic compound are investigated using X-ray diffraction and magnetic measurements and compared with the properties of the SmFe2 compound. It is established that the partial substitution of Y for Sm in SmFe2 leads to the decrease in both the Curie temperature TC and the two spin-reorientation transition temperatures TSR1 and TSR2. The complex behavior of the field and temperature dependencies of the longitudinal, transversal, anisotropic and volume magnetostriction in a wide temperature range (including the spin-reorientation region) is discussed in terms of the single-ion anisotropy and magnetostriction theory. The influence of other factors, such as peculiarities of the state of Sm3+ ions and competition between contributions to magnetostriction from the iron and samarium sublattices, is also considered.

This paper presents the study of the magnetic properties and magnetocaloric effect (MCE) of the rare-earth ferrimagnetic Dy 2 Fe 10 Al 7 compound. The field and temperature dependencies of the magnetization in the temperature range 4.2–300 K were studied in magnetic fields up to 100 kOe. The MCE was studied by direct method in magnetic fields up to 70 kOe. It was established that the sign of the MCE changes from positive to negative near the compensation temperature. It was shown from the obtained experimental results and the theoretical estimations that the temperature and field dependencies of the MCE in rare-earth ferrimagnet differ from those in ferromagnetic materials. The effective field ( H eff 2 ) determined from the values of the MCE near to the compensation temperature are in a good agreement with those reported earlier.

The multicomponent Sm0.2(Tb,Y)0.8Fe2 system was obtained by the arc melting method, in which atoms with a high magnetic moment of terbium are replaced by yttrium atoms that do not carry a noticeable magnetic moment. In this system, varying not only the composition, but also external factors (temperature, magnetic field, etc.), it is possible to influence competing exchange interactions and observe a number of unique phenomena, such as, for example, the phenomenon of magnetic compensation. Using the method of high-temperature and low-temperature X-ray diffraction, the phase composition and atomic-crystalline structure of the Sm0.2(Tb1-xYx)0.8Fe2 alloys (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were studied. The temperature dependences of the unit cell parameters were obtained in a wide temperature range from 80 to 700 K. Thermal expansion was investigated by strain-gauge method. The temperatures of magnetostructural phase transitions are determined, and a magnetic phase diagram is constructed.

The series of ferrimagnetic Laves-phase compounds ( Tb , Y ) 0.8 Sm 0.2 Fe 2 obtained by gradual substitution of yttrium for terbium as well as the hydrides (Tb,Y)0.8Sm0.2Fe2 H 3.7 (amount of hydrogen close to the maximum allowed by the structure type) are investigated. We find that the MgCu2-type crystal structure is preserved after hydrogenation while the unit cell volume increases by ∼28%. The Curie temperature ( T C ) of hydrides is almost half the T C ’s of the parent compounds. For ( Tb 1 − x Y x ) 0.8 Sm 0.2 Fe 2 with Y concentration x = 0.6 , we observe a magnetic compensation, i.e. mutual cancellation of magnetic moments of the sublattices, which is fully consistent with the model of a three-sublattice collinear ferrimagnet. In the hydrides (Tb1-xYx)0.8Sm0.2Fe2 H 3.7 the magnetic compensation occurs at x = 0.2 . In this case, we argue that a non-collinear magnetic arrangement is placement in the compound. We demonstrate that hydrogenation is a simple tool of changing the composition for which the phenomenon of magnetic compensation occurs.

The paper presents the results of the study of magnetic and magnetostrictive properties of rare-earth intermetallides based on TbFe2 compound: Tb1-xZrxFe2, Tb1–xSmxFe2 and (Tb1–xYx)0.8Sm0.2Fe2. These alloys have a cubic crystal structure of the Laves phase C15 throughout the substitution region. For the system of alloys Tb1–xZrxFe2 the single-phase area is limited to the replacement parameter 0 < x < 0.2 and 0.8 < x < 1.0. The compounds of the Tb1–xSmxFe2 system were studied via X-ray dilatometry. The magnetostriction of alloys within the Tb1–xZrxFe2 and (Tb1–xYx)0.8Sm0.2Fe2 systems was studied in the temperature range of 80-320 K in magnetic fields of up to 17 kOe via a strain-gauge method. It was found that each system has the phenomenon of sign inversion of magnetostriction constants: in the system Tb1–xZrxFe2 in the area of replacement parameter x = 0.8, in Tb1–xSmxFe2 - in the area x = 0.45, and in the system of alloys (Tb1–xYx)08Sm02Fe2 at x = 0.6. It was demonstrated that magnetic compensation and spin reorientation phenomena occur in these systems. The obtained results are discussed in the model of alloys with competing exchange interactions.

The melt-spun Y2(Fe,Mn)17ribbons were synthesized by rapid quenching from the melt. The phase composition, crystal structure and magnetocaloric effect (MCE) in low-cost iron-based pseudo-binary Y2(Fe,Mn)17ribbons were investigated respectively by using x-ray diffraction and direct measurements of MCE. It was found that crystal structure of the as-spun ribbons retains hexagonal Th2Ni17-type because of the weak glass-forming ability. The Y2Fe14Mn3and Y2Fe13Mn4nanostructured ribbons demonstrate higher MCE compare to polycrystalline alloys.

Synthesis of nanocrystalline and microcrystalline dysprosium was carried out. Temperature and field dependences of magnetocaloric effect were performed by direct method in field up to 1.2 T and temperature range 80-190 K. It was found that the nanocrystalline state leads to a significant reduction of the magnetic phase transition temperatures and to a small increase of the maximum value of the magnetocaloric effect in dysprosium. It is associated with the large amount of interface atoms in nanocrystalline Dy ribbons with a lower number of the nearest-neighbor atoms, causing the magnetic phase transition temperature decrease. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A systematic study is made of the magnetic properties of the hydrides of Y2Fe17−xMnxHy intermetallic alloys (0 ⩽ x ⩽ 8 and 0 ⩽ y ⩽ 4.4 at.H/f.u.) and the exchange interaction parameters of these compounds are estimated. It is found that hydrogen atoms enhance the ferromagnetic interactions. The decrease of the Curie temperature observed in both hydrides and parent alloys with substitution of manganese for iron gives an indication of the reinforcement of negative exchange interactions. As a result the magnetic order of the compounds under study is subject to change at high (x > 6) manganese concentration. The transformation of magnetic state in the Y2Fe17−xMnx-H system is explained on the basis of molecular field theory connecting the Curie temperatures with the value and sign of exchange interaction integrals (AFeFe, AMnMn, and AFeMn) for magnetoactive atoms: iron and manganese.

The effect of an external magnetic field with a strength up to 140 kOe on the phase transitions in manganese arsenide single crystals has been investigated. The existence of unstable magnetic and crystal structures at temperatures above the Curie temperature T C = 308 K has been established. The displacements of manganese and arsenic atoms during the magnetostructural phase transition and the shift in the temperature of the first-order magnetostructural phase transition in a magnetic field have been determined. It has been shown that the magnetocaloric effect in a magnetic field of 140 kOe near the Curie temperature T C is equal to ΔT ∼ 13 K. A model of the superparamagnetic state in MnAs above the temperature T C has been proposed using the data on the magnetic properties and structural transformation in the region of the first-order magnetostructural phase transition. It has been demonstrated that, at temperatures close to T C, apart from the contribution to the change in the entropy from the change in the magnetization there is a significant contribution from the transformation of the crystal lattice due to the magnetostructural phase transition.

The MCE in MnAs and doped Mn (As,Sb) compounds with low concentration of Sb has been studied by direct investigation. It was shown that for MnAs the maximum value of MCE is ΔT = 0.28 K on heating (at 308 K) and ΔT = 0.88 K on cooling (at T = 306 K) in magnetic filed 12.5 kOe. In doped Mn (As,Sb) compounds the temperature dependence of MCE is similar to MnAs. All investigated compounds demonstrate a strong temperature and field hysteresis of magnetic properties in magnetic field less than 40 kOe. It was established that a small concentration of Sb leads to decrease of MCE hysteresis and preserves the phase transition at room temperature region.

Under the terms of the Creative Commons Attribution 3.0 Unported License., An investigation of the Y2Fe17 compound belonging to the class of intermetallic alloys of rareearth and 3d-transition metals is presented. The magnetization, magnetostriction, and thermal expansion of the Y2Fe17 single crystal were studied. The forced magnetostriction and magnetostriction constants were investigated in the temperature range of the magnetic ordering close to the room temperature. The giant field induced volume magnetostriction was discovered in the room temperature region in the magnetic field up to 1.2 T. The contributions of both anisotropic singleion and isotropic pair exchange interactions to the volume magnetostriction and magnetostriction constants were determined. The experimental results were interpreted within the framework of the Standard Theory of Magnetostriction and the Landau thermodynamic theory. It was found out that the giant values of the volume magnetostriction were caused by the strong dependence of the 3delectron Coulomb charge repulsion on the deformations and width of the 3d-electron energy band., The work was supported by RFBR Grant Nos. 13-02-00916 and 12-02-31516.

Magnetization and anisotropy field of Nd2Fe14−xCoxBH4.1 (x=0–8) hydrides have been measured on powder aligned specimens. It was found that the unit cell volume increases after hydrogenation. At room temperature all compounds show “easy axis” anisotropy and “easy cone” anisotropy at temperatures below the spin-reorientation temperature (TSR). TSR of the initial compounds and hydrides decreases by the replacement of Fe by Co. Hydrogen insertion in the crystal lattice of Nd2Fe14−xCoxBH4.1 leads to a decrease of TSR by 15 K at Co concentrations x ⩽ 6 . The anisotropy field at room temperature decreases under hydrogenation. We can conclude that the replacement of Fe by Co causes both the unit cell volume and TSR decrease. The TSR decrease is determined by a change of electron structure and magnetocrystalline anisotropy rather than by a decrease of the unit cell volume with the Co concentration increasing.

Magnetocrystalline anisotropy and spin-reorientation transitions (SRT) of the ErFe 11− x Co x TiH y ( x = 0 , 2, 4; y = 0 , 1) compounds with the ThMn 12 -type structure were studied. The investigation of ErFe 11− x Co x TiH y compounds with x ≤ 2 show an “easy axis” anisotropy at room temperature and an “easy cone” anisotropy at temperatures below the spin-reorientation temperature ( T SR ). The ErFe 7 Co 4 Ti with x = 4 below the SRT exhibits an “easy plane” anisotropy with the easy direction oriented along the [1 0 0] axis. Hydrogen insertion into ErFe 9 Co 2 Ti leads to an increase of T SR whereas hydrogenation of ErFe 7 Co 4 Ti causes T SR decreasing down to 40 K and essential change of SRT character. ErFe 7 Co 4 TiH hydride has an “easy cone” anisotropy below T SR . It was found that the replacement of the Fe by Co and hydrogen insertion into the crystal lattice of Er(Fe,Co) 11 Ti compounds has an opposite influence on the SRT temperature.

Effect of the hydrogen absorption on the magnetic properties of a Ce2Fe16Mn single crystal has been investigated in magnetic fields up to 140 kOe and in the temperature range 1.7–300 K. A metamagnetic transition from the helical antiferromagnetic structure into the ferromagnetic phase was observed. The temperature dependence of the transition critical field HCR(T) has a maximum at 130 K. Hydrogenation leads to suppressing of the antiferromagnetic state. The relationship between the magnetic properties of the Ce 2Fe16Mn compound and the unit cell volume upon hydrogenation has been analysed. © 2003 Elsevier B.V. All rights reserved.

Magnetic characteristics of the Nd 2 Fe 14 BH x single crystals and polycrystalline samples were investigated in the temperature range 4.2-750 K. It is established that hydrogen absorption does not change the crystal structure of these compounds but is accompanied by an expansion of a unit cell volume. The obtained data show that the Curie temperature and magnetic moment are increasing in the all investigated hydrides whereas the temperatures of a spin-reorientation transition remain unchanged.

The structure and magnetic properties of RFe11TiN compounds (R=Gd or Lu) containing nitrogen are investigated. Magnetic measurements are performed on a magnetometer in magnetic fields up to 100 kOe in the temperature range from 4.2 to 750 K with the use of RFe11TiN single crystals, RFe11TiN powders placed in a ceramic cell, and samples oriented in an external magnetic field. It is found that the nitridation leads to an increase in the Curie temperature and the saturation magnetization. The samples studied are uniaxial over the entire temperature range of magnetic ordering. The magnetic anisotropy decreases upon nitridation. It is demonstrated that, within the local anisotropy model, the decrease in the magnetic anisotropy constant K1 can be explained by the redistribution of the electron density in the vicinity of the crystallographic positions occupied by iron atoms.

The structural and magnetic characterization of Lu2Fe17Hx (x=0; 3) single crystals is presented. The host alloy crystallizes with a disordered variant of hexagonal (Th2Ni17-type P63/mmc) structure. It is observed that the host alloy symmetry is retained upon hydrogenation. Hydrogen is found to be accommodated in the rare earth-rich octahedral position. The Neel temperature of the hydride Lu2Fe17H3 is increased by 35 K per hydrogen atom. The magnetization and magnetic anisotropy constant remains practically unaffected in the hydride Lu2Fe17Hx at x=3.

The magnetic anisotropy and magnetostriction of a Lu2Fe17 single crystal are investigated. The temperature dependence of the magnetic anisotropy constant K 1 is measured in the range 4.2–300 K. The results obtained are compared with the data calculated using the Callen theoretical formula. It is found that the temperature dependence of K 1 for the Lu2Fe17 single crystal deviates from the temperature curve predicted by the localized single-ion model. The inference is drawn that a certain contribution to the magnetic anisotropy of the Lu2Fe17 compound is made by the magnetic anisotropy of band electrons. The longitudinal, transverse, and volume magnetostrictions of the Lu2Fe17 single crystal are studied, and the magnetostriction constants are calculated. It is demonstrated that the exchange integral of Lu2Fe17, as for the Y2Fe17 compound, substantially depends on the atomic volume. This dependence is responsible for the considerable difference between the Curie temperatures of the Lu2Fe17 and Y2Fe17 compounds. It is revealed that the magnetostriction of the Lu2Fe17 single crystal in the temperature range of the magnetic phase transition is determined by the two-ion exchange and single-ion contributions.

Magnetic anisotropy of LuFe 11 TiH x (x=0, 1) single crystals and magnetically oriented powder samples of LuFe 11 TiN x ( x =1) were investigated. The anisotropy study has been performed by means of torque and magnetization measurements. The temperature dependencies of the magnetocrystalline anisotropy constants were determined using both least-squared fitting for the corrected experimental torque curves and from the magnetization isotherms along the hard [1 0 0] direction using the Sucksmith–Thompson relation. The lattice parameters, Curie temperature and saturation magnetization are increased by both hydrogenation and nitrogenation. The easy c -axis anisotropy is enhanced in the hydrides but decreased in the nitrides. The volume expansion and change of local environment of Fe ions after hydrogenation and nitrogenation lead to the effects observed.

The magnetic anisotropy and spin-reorientation phase transitions in single crystals of the RFe11Ti (R=Lu, Ho, and Er) compounds and their hydrides are investigated. Measurements are carried out on capacitance and torque magnetometers. The magnetic anisotropy constants K1 and K2 are determined by the mathematical processing of experimental magnetization curves in terms of the phenomenological theory of the anisotropic ferromagnet magnetization. It is demonstrated that the hydrogenation strongly affects the magnitude and the sign of magnetic anisotropy constants, as well as the spin-reorientation phase transitions. The hydrogenation of the HoFe11Ti compound leads to the change in sign of the magnetic anisotropy constant K1. The inference is made that a change in the atomic volume and the axial ratio c/a cannot result in the observed effects. A change in the magnetic anisotropy constants upon hydrogenation is primarily due to the change in the interaction of the quadrupole moment of a 4f electron subshell of rare-earth ions with surrounding ions of the crystal lattice and also with valence and conduction electrons.

The magnetic properties of Lu 2 Fe 17 single crystal have been studied by means of magnetization, susceptibility and magnetostriction measurements. The unusual magnetic behavior with two magnetic phase transitions has been observed in magnetic fields up to 50 Oe. The magnetostriction of the Lu 2 Fe 17 compound has the maximum at temperature T ≈285 K at which the paraprocess makes the main contribution to the magnetization.

Single crystals of TbFe11Ti and its hydride with tetragonal ThMn12-type structure were obtained. Magnetostriction measurements have been made on TbFe11TiHX (x=0, 1) single crystals by the applied strain gauge method in the temperature range from 77 to 400 K and in magnetic fields up to 13 kOe. Magnetization measurement along the main crystallographic directions of the tetragonal structure have been performed on RFe11TiHx (x=0, 1) single crystals in applied high magnetic fields up to 120 kOe in the temperature range from 4.2 to 300 K. It was concluded that hydrogenation results in an increase in rare-earth anisotropy that leads to the disappearance of the spin-reorientation transition in the TbFe11TiH single crystal. Hydrogenation lead to a change in sign of the magnetic anisotropy constant K3 and the magnetostriction constant λ2α,2.

The magnetostrictions of polycrystalline LaCo13, LaCo13H3.5 and LaCo13N3 compounds were measured in temperature range from 78 to 350 K in magnetic fields up to 13 kOe. It was shown that hydrogenation and nitrogenation are methods of regulation of the magnetostriction in LaCo13 compounds.

The field, temperature, and angular dependences of longitudinal λ‖ and transverse λ⊥ magnetostriction in single-crystal DyFe11Ti are investigated. Tensometric measurements were made in the temperature range from 78 to 300 K in magnetic fields up to 12 kOe. Measurements of the magnetostriction of single-crystal DyFe11Ti, YFe11Ti, and LuFe11Ti imply that the sublattice of 3d transition metals makes only a small contribution to the magnetostriction in compounds RFe11Ti, and that the primary contribution to the magnetostriction of these compounds comes from the rare-earth metal sublattice. The primary microscopic mechanism for magnetostriction is single-ion magnetostriction caused by the interaction of the anisotropic orbital electron cloud around the Dy3+ magnetic ion with the crystal field of the lattice.

Single crystals of TbFe11-xCoxTiHy (x = 5; y = 0, 1) with the tetragonal ThMn12-type structure were obtained. Magnetisation measurements along main crystallographic directions of TbFe6Co5TiHy (y = 0, 1) single crystals have been performed in the temperature range 5-340 K. It was established that TbFe6Co5Ti compounds show "easy axis" anisotropy in whole temperature range below Curie temperature (TC). It was concluded that hydrogenation leads to an increase of magnetic anisotropy, and TbFe6Co5TiH hydride demonstrates "easy plane" anisotropy with the easy axis oriented along the [100] crystallographic direction. It was found that the replacement of the Fe by Co and hydrogen insertion into the crystal lattice of Tb(Fe,Co)11Ti compounds have an opposite influence on the magnetocrystalline anisotropy.

Summary form only given. The insertion of the light interstitial elements (hydrogen and nitrogen) into the RFe/sub 11/Ti (R is rare-earth metal) crystalline lattice results in an apparent change of the rare-earth intermetallic compounds magnetic properties. The hydrides and nitrides of these compounds retain the ThMn/sub 12/ type structure of the parent alloys, however interstitial modification leads to a volume expansion, which is main cause for the improvement of Curie temperature (T/sub C/) and saturation magnetization. The change from easy plane to easy axis magnetic anisotropy for the RFe/sub 11/TiN/sub x/ (R=Tb, Dy) is ascribed to modification of the rare-earth crystal field due to the surrounding nitrogen atoms. Another example of interstitial modification is a nitriding of the easy axis SmFe/sub 11/Ti, whose nitride SmFe/sub 11/TiN shows easy-plane anisotropy. The crystal field in Sm/sub 2/Fe/sub 17/N/sub 3/ and SmFe/sub 11/TiN has been investigated by Skomski et al. (1993). The aim of our work is to study the effect of interstitial hydrogen on the rare-earth crystal field in SmFe/sub 11/TiH single crystal, based on single ion anisotropy model and to compare it with the effect of interstitial nitrogen atoms on the SmFe/sub 11/TiN.

We present a study of the hydrogenation effect on structural and magnetic properties of ${\mathrm{HoFe}}_{11}\mathrm{Ti}$ single crystal. Single crystal hydride ${\mathrm{HoFe}}_{11}{\mathrm{TiH}}_{X}$ with H concentration $x=1$ at. H/f.u. has been prepared. Magnetization measurements along the main symmetry directions of the tetragonal structure have been performed on ${\mathrm{HoFe}}_{11}{\mathrm{TiH}}_{x}$ $(x=0,1)$ single crystals at applied high magnetic fields up to 80 kOe in the temperature range from 4.2 to 300 K. Torque measurements were carried out in the temperature range 78--700 K in magnetic fields up to 13 kOe. The single-ion magnetic exchange and crystalline-electric-field interaction model has been applied to the fitting of the experimental behavior of the single-crystal ${\mathrm{HoFe}}_{11}{\mathrm{TiH}}_{x}$ $(x=0,1)$ samples. A set of CEF parameters and mean exchange field has been obtained. Hydrogen atoms have been found to have a significant effect on the second-order crystal field parameter ${A}_{2}^{0}$ ${(A}_{2}^{0}=\ensuremath{-}20.5$ ${\mathrm{Ka}}_{0}^{\ensuremath{-}2}$ for ${\mathrm{HoFe}}_{11}\mathrm{Ti}$ and ${A}_{2}^{0}=\ensuremath{-}118$ ${\mathrm{Ka}}_{0}^{\ensuremath{-}2}$ for ${\mathrm{HoFe}}_{11}\mathrm{TiH}).$

The magnetic structure of single-crystal TbFe11−xCoxTi compounds has been studied over a broad temperature range and in strong magnetic fields (up to 14 T). Measurements of magnetization and magnetostriction and a study of the domain structure revealed that spin-reorientation transitions (SRTs) in TbFe11−xCoxTi single crystals depend substantially on the cobalt concentration. It was established that the SRT temperatures and threshold magnetic fields are governed by the interplay between the magnetic anisotropies of the 3d and terbium sublattices. It is shown that, in these compounds, the low-temperature phase with planar anisotropy is separated in temperature from the high-temperature phase with uniaxial anisotropy by an intermediate metastable phase containing domains of the uniaxial or planar phase.

The magnetocaloric effect of rare-earth metals (REMs) Gd, Tb, and Dy in the nanostructured state is investigated. The ranges of working temperatures and cool capacity for materials based on nanocrystalline REMs are calculated from the experimental data. These results enable us to evaluate in detail the magnetic properties of REMs in a nanocrystalline state. It is shown that nanocrystalline Dy possesses the largest cool capacity, making this material most effective for magnetic cooling in the temperature range of 82–134 K.