The magnetothermal properties of the quaternary Fe49Rh46.1Pd3.1Ir1.8 alloy are investigated by a combination of first-principles calculations, structural characterization, magnetometry, calorimetry, and direct measurements of the adiabatic temperature change. An exceptional magnetocaloric response is obtained, with ΔTad reaching −11.9 K in a field of 1.85 T under the discontinuous protocol and −8.6 K under the continuous (cyclic) protocol, both values exceeding those reported to date for FeRh-based alloys under comparable conditions. The enhancement originates from a combination of structural and electronic properties: a nearly single-phase B2 composition, induced magnetic moments on Pd and Ir predicted by first-principles calculations, and a narrow magnetostructural transition (∼6 K). In addition, the present composition exhibits an exceptionally small thermal hysteresis of ∼6 K, which is among the smallest reported for the FeRh family and preserves a large magnetocaloric response under cyclic operation. The high transition temperature of ∼411 K further distinguishes the present composition from conventional near-room-temperature magnetocaloric systems. The temperature dependences of the lattice parameter, magnetization, heat capacity, and magnetocaloric response are presented and compared with literature data for binary and ternary FeRh-based alloys.

The X-ray Rietveld method has been used to refine the structure, determine the lattice periods, and study the phase composition of the samples of multicomponent polycrystalline solid solutions TbCo _(2-x) Inx (х = 0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.3, 0.35, 0.4), which are characterized by large values of magnetostriction saturation. With an increase in the indium concentration, the content of the TbCo2 phase with a Laves phase structure decreases, the content of the TbCo3 phase increases, and a Tb11Co4In9 phase is formed. The lattice period in the TbCo2 compound (sp. gr. Fd 3̅ m) changes nonlinearly: increases in the range of x = 0–0.1 from a = 7.209(8) Å to a = 7.216(1) Å due to the replacement of cobalt atoms with indium atoms, having a larger radius. Then, in the concentration range of x = 0.15–0.4, it decreases to a = 7.205(1) Å at х = 0.4 due to the replacement of terbium atoms with indium and formation of structural defects.

Abstract—Multicomponent polycrystalline TbInxCo2 – x (with х = 0–0.2) solid solutions are prepared for the first time, and their crystal structure and magnetic, magnetocaloric, and magnetostrictive properties are studied. X-ray diffraction patterns taken at room temperature demonstrate mainly the presence of the cubic C15 Laves phase in all samples. As the indium content increases to x = 0.1, the lattice parameter is found to increase; the further increase in the indium content to х = 0.2 leads to a decrease in the lattice parameter. In this case, the Curie temperature TC monotonically increases to 245 K. The isotheral magnetic entropy change ΔSmag is calculated in accordance with magnetic measurements using the thermodynamic Maxwell’s relation. At a magnetic field change from 0 to 1.8 T, the maximum entropy change monotonically decreases and, for composition with x = 0.2, is 1.8 J/(kg К). As the indium content increases to x = 0.05, the volume magnetostriction increases. The further increase in the indium concentration leads to the decrease in the peak values and their shift to high temperatures.

The crystal structure, magnetic and magnetostrictive properties of the Laves phases Tb 0.16 Ho 0.84 Fe 2-x T x (T = Co, Ni, x = 0.1, 0.2, 0.3, 0.4) are investigated. Polycrystalline samples were prepared by induction melting with subsequent homogenizing annealing. The studied compounds crystallize in a structure of the MgCu2 type. Partial substitution of iron by Co and Ni leads to a decrease in the parameter and volume of the unit cell by ~3%. The Curie and spin reorientation temperatures of the studied compounds were determined, magnetic phase diagrams were constructed. Compounds with high values of saturation magnetostriction and magnetostrictive susceptibility in the temperature range of 190-320 K were found.

This work presents the results of a comparative analysis of the thermal, magnetic, magnetocaloric and magnetostrictive properties of the Dy0.42Ho0.42Tb0.16Co2, Dy0.5Ho0.5Co2 and TbCo2 compounds. All studied compounds have the MgCu2-type Laves phase structure at room temperature. Dy0.5Ho0.5Co2 and TbCo2 demonstrate first- and second-order transitions from a paramagnetic state to a magnetically ordered one, respectively. Special attention is given to determining the order of magnetic phase transition in a multicomponent compound with three rare earth elements (Tb, Dy and Ho). Features of the magnetocaloric effect and magnetostriction of (Tb,Dy,Ho)Co-2 compounds have been studied in magnetic fields up to 14 T and in wide temperature range (4.2 - 300 K). The joint manifestation of significant magnetocaloric and magnetovolume effects at the Curie temperature can be useful for a variety of technical applications.

The aim of the work was to create highly efficient materials for solid-state magnetic cooling at temperatures below room temperature (120–280 K). For this, new (R,R')(Co,T)2 and R(Mn,T)Si (T = Fe, Co, Al) compounds with a noticeable magnetocaloric effect (MCE) in the Curie temperature region were investigated. The main regularities of the behavior of the MCE depending on the composition are revealed.

The characteristics of materials with high magnetostrictive properties have been studied and described. The object of study is pseudo-binary compounds RFe 2 (R = rare earth element) with a cubic Laves structure. The characteristics of the structure and magnetic properties of substituted (Tb, Nd)Fe2 alloys are presented, the structure is refined, the lattice parameters and phase composition are determined.

In this work, polycrystalline samples of hard-magnetic materials of (Nd1-xPrx)(2)Fe14B general formula have been prepared and subjected to severe plastic deformation (SPb). hereafter the features of nanostructure formation in the compounds were investigated before and after SPD using atomic force microscopy and magnetic force one (AFM & MFM). The differences in texture formation were revealed when studying the surface microstructure of both the initial and deformed samples. The initial ones prepared by the Czochralski method, exhibited the columnar structure, while the SPD samples exhibited the concentric rings containing elongated nanosized crystallites. The magnetic domain structure was visualized using the MFM that clearly demonstrated the relationship between the microstructural features and the magnetic domains' configuration.

The crystal structure and magnetic properties of multicomponent compounds $\text{Ce}_{1-x}\text{Tb}_{x} \text{Fe}_{2}$ ($x$ = 0, 0.1, 0.2, 0.3, 0.5, 0.7) are studied in this letter. Compounds crystallize in a structure of the MgCu2 type; the content of the second phase (PuNi3-type, R3m space group) averaged 5%–8%. The parameters of the unit cell were determined and the surface of the sample was investigated by atomic force and magnetic force microscopy. In the temperature range 90–600 K, the magnetization of the alloys was investigated, and the Curie temperature was determined. Information was obtained on the magnetocaloric and magnetostrictive properties of the compounds under study.

The magnetocaloric effect (MCE) and anomalies of magnetostriction behavior were studied at the order-order and order-disorder magnetic phase transitions in hydrided Gd single crystal grown by a modified Czochralski method. The composition GdH0.15 was obtained using a Sievert-type apparatus. While parent Gd shows an isotropic MCE at the order-disorder phase transition, the effect is anisotropic in GdH0.15 due to the appearance of local anisotropy. We investigate in detail the temperature variation of the longitudinal, transverse, volume, and anisotropic magnetostriction. Hydrogenation is found to influence both the magnitude and the sign of the magnetostriction constants $\lambda_{\rm ij}^{\alpha}$.

In this work the magnetocaloric effect in the TbCo2-H system in the region of the Curie temperature was studied both by direct and indirect methods in external magnetic fields up to ~1.4 and 14 T, respectively. We have paid special attention to the magnetic and magnetothermal properties of the TbCo2–H with high hydrogen content. The mechanisms responsible for the change in the Curie temperature were established, and the field and temperature dependences of the magnetocaloric effect were analyzed in detail. In addition, the magnetocaloric properties (including critical parameters) for various systems based on the TbCo2 compound were compared. The main regularities of the change in the MCE value and the Curie temperature depending on the composition are discovered and discussed.

In this work, we perform a comparative study of the magnetization behavior of four series of compounds R 2 Fe 14 B and their hydrides R 2 Fe 14 BH 5.5 , and the compositions (Nd 0.5 R 0.5 ) 2 Fe 14 B and their hydrides (Nd 0.5 R 0.5 ') 2 Fe 14 BH 5.5 with R and R' = Ho, Er, and Tm. The magnetization is measured in pulsed magnetic fields up to 58 T and in megagauss fields up to 135 T at 5 K. The first and second critical fields of the field-induced transitions, H c1 and H c2 were estimated analytically and the results were verified against experimental data. We find that hydrogenation of R 2 Fe 14 B and (Nd 0.5 R 0.5 ') 2 Fe 14 B reduces drastically the H c1 and H c2 values and, as a consequence, the intersublattice R-Fe exchange interaction parameter λ.

The magnetic properties of polycrystalline samples of isotopically enriched iron with the content of isotope Fe-56 99.945 +/- 0.002 at. % were investigated at different magnetic field strength values. The samples of monoisotopic iron were melted in the environment of argon and annealed in hydrogen. The same measurements were carried out on the samples of iron with natural isotopic composition. The quantity and composition of impurities in the samples of natural and monoisotopic iron were equal. The magnetic properties were measured using an automatic induction vibro-magnetometer MagEq MNMS 216 and an automatic measuring complex MK-3E in accordance with GOST 8.377-80 and GOST 12119.1-98. It was found that the value of the saturation magnetization J(s) of Fe-56 is higher by 10.87% than that of Fe-nat at room temperature, and by 11.35% at 100 K. The values of saturation induction B-s and residual magnetic induction Br for Fe-56 are higher than for Fe-nat. The difference in the values of the coercive force H-c for the Fe-nat and Fe-56 samples is due to the difference in the grain size of the samples and in the purity of the materials.

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.

Polycrystalline TbxDy1-xR0.1Fe2-zCoz (R = Nd, Pr, x = 0.2, 0.3; z = 0, 1.3) cubic Laves phase alloys with MgCu2-type structure were prepared by arc melting followed by homogenizing annealing. The crystal structure, magnetic properties, and magnetostriction have been investigated. Compounds with high values of magnetostrictive susceptibility were found in the temperature range 150-300 K. Compounds with partial substitution of cobalt for iron demonstrate a change in the sign of anisotropic magnetostriction. This work continues the search for magnetostrictive materials with inexpensive neodymium and praseodymium.

The multicomponent Sm 0.2 (Tb,Y) 0.8 Fe 2 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 Sm 0.2 (Tb 1-x Y x ) 0.8 Fe 2 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.

In this paper, the full magnetization process demonstrated by the series of ferrimagnetic intermetallic compounds ${(\mathrm{Nd},\mathrm{Ho})}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ and ${\mathrm{Ho}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ and their hydrides with the maximum possible hydrogen content (for the given crystal structure type) is studied theoretically and experimentally using megagauss magnetic fields. We observe field-induced phase transitions from the initial ferrimagnetic to the forced-ferromagnetic state in magnetic fields up to 130 T and describe the magnetization process analytically. We find a drastic decrease of the critical transition fields in the hydrogenated compounds. This is due to extremely strong, nearly twofold reduction of the $R$-Fe intersublattice exchange interaction because of the combined substitution and hydrogenation effects. A comparative analysis of the magnetization behavior for the system ${\mathrm{Ho}}_{2}{\mathrm{Fe}}_{17}\text{\ensuremath{-}}\mathrm{H}$ is also performed.

Magnetic force microscopy (MFM) and magnetometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to study the magnetic and structural properties of the (Nd,Pr)-Fe–B and (Nd,Ho)-(Fe,Co)-B alloys. The alloys are synthesized using an arc or induction furnaces. The nanocrystalline state of the (Nd,Ho)-(Fe,Co)-B alloys is reached by two techniques, namely, melt spinning (MS) and severe plastic deformation (SPD). Hydrogenation and multistage treatment of (Nd,Ho)-(Fe,Co)-B alloys, which includes severe plastic deformation of melt-quenched ribbons and subsequent heat treatment, is also used. The surface morphology and domain structure of samples are studied. These pictures are used to interpret the observed magnetic hysteresis loops of the samples. It was found that multistage treatment allows one to obtain samples with higher values of coercivity due to the formation of a special microstructure with oval grain (the aspect ratio equal to ∼ 3).

A comprehensive study of the structure and phase composition, magnetostrictive and magnetic properties of the (Sm0.5R0.5)Fe2 (R = Gd, Tb) compounds was performed. The effect of partial replacement of samarium by gadolinium and terbium on the microstructure of the surface, the temperature of phase transitions, the magnitude of magnetostrictive deformations and magnetization was studied. Using atomic force and magnetic force microscopy, the surface topology at the micro and nanoscale was established, and information on the magnetic domain structure at room temperature was obtained.