The interaction of magnetic materials R2Fe17 (R = Gd, Dy, Lu) with hydrogen at 473 and 523 K and hydrogen pressure up to 5 MPa was studied by the Calvet calorimetry method. The dependences P = f(C) and ∆H = f(C) were obtained (P is the equilibrium pressure of hydrogen, ∆H is the enthalpy of absorption/desorption, C is the concentration of hydrogen in an intermetallic compound (IMC), C = H/IMC). It has been established that the enthalpy values of the reaction of hydrogen with IMC change with changes in the process temperature, the concentration of hydrogen in the metal matrix, as well as during the transition from one compound to another. The graphs of the dependence ∆H = f(C) show two sections where the enthalpy values are constant. It is assumed that the observed changes in the thermodynamic parameters of the process are related to the filling order of octahedral interstices 9e and tetrahedral interstices 18g, and the filling process of octahedral interstices 9e occurs in two stages with different energy characteristics.

We demonstrate the peculiarities of the magnetization process in the ferrimagnetic intermetallic compounds of the (R,R')(2)Fe14B-type, their hydrides, as well as complex modified rare earth compounds (R,R')(2)Fe14B (R = Nd, Gd, Dy, Ho). They have been studied theoretically and experimentally in ultrahigh magnetic fields. We observe phase transition induced by external ultrahigh magnetic fields (up to 200 T) and also describe the magnetization process analytically (in terms of critical transition fields) and numerically. In this work, the first and second critical fields of the field-induced magnetic transitions, H-c1 and H-c2, were estimated. Critical field H-c2 predicting the place of transition to the forced-ferromagnetic state was estimated for the first time for various intermetallic compounds.

The effect of substitutional 4f-elements on the magnetism of rare-earth compounds RFe2-type with the Laves phase structure is studied to find new multifunctional materials, as well as to define the macro- and microscopic parameters of multicomponent magnets. The crystal structure of (Er,Y,Sm)Fe2 compounds is investigated by X-ray powder diffraction. Detailed information on the magnetic properties of the iron sublattice for multicomponent compounds with three different rare-earth elements is obtained for the first time by means of the 57Fe Mössbauer spectroscopy. The main regularities in the magnitude variation of magnetocaloric effect and magnetostriction (linear, anisotropic and volume) in varying composition of the (Er,Y,Sm)Fe2 compounds are determined.

The paper presents a comparative study of the magnetocaloric characteristics of rare-earth magnets. Both hydrogen containing systems Gd–H, (Gd,R)Ni–H (R is a rare-earth metal) and RCo2–H with a Laves phase structure and systems without hydrogen, such as layered magnets with the general formula RTX (T = Mn, Fe, Co; X = Si), are studied, as well as compounds of the type R2(Fe,T)17 (T = Al), which have a magnetic compensation point and exhibit an alternating magnetocaloric effect (MCE). The MCE was measured directly and indirectly from the analysis of the field dependences of magnetization. The main regularities and specific features of the formation of magnetocaloric properties of materials depending on their composition and structure have been revealed.

Combination of double exposure scanning strategy and low-melting Nd70Cu30 eutectic phase addition approaches was investigated to improve laser powder bed fusion of Nd2Fe14B-based hard magnetic material. Technological route of Nd2Fe14B + Nd70Cu30 powder mixture was developed to obtain initial material with proper morphology and characteristics for subsequent 3D-printing. Effect of the mentioned combination on structure of the formed material and its magnetic properties was studied. Improvement of printed material density up to 98.8 % and defectiveness reduction were shown. Three different types of areas were found in the structure of the synthesized material with variable neodymium, copper and iron content. Distribution of copper throughout the whole structure of the material showed the difference of the proposed approach with convenient grain boundary infiltration technique. More stable melting, quality of printed material and less deviations of magnetic properties were achieved due to the applied approach.

New (Er1 – xYx)0.8Sm0.2Fe2 multicomponent alloys with a substitution parameter of x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0 are synthesized and their atomic crystal structure and magnetic properties are studied. It is shown that full magnetic compensation can be expected in the region of 0.2 < xcomp < 0.4. Er0.8Sm0.2Fe2 alloy exhibits temperature-dependent magnetization compensation at Tcomp = 400 K.

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.

We have conducted the study of structural, magnetic, magnetothermal, and magnetoelastic properties of four rare-earth compounds: Gd4.5Tb0.5Si2Ge2, Gd4TbSi2Ge2, Gd4.4Tb0.5Ti0.1Si2Ge2, and Gd3.9TbTi0.1Si2Ge2 in the vicinity of magnetically induced phase transitions. We demonstrate that the introduction of Ti into the rare-earth sublattice separates the structural and magnetic phase transitions and changes the order of magnetic phase transition from type I to II, while preserving high values of magnetocaloric effect (MCE). Additionally, incorporating a small quantity of Tb enables the creation of compounds with enhanced MCE values over a specific temperature range of 240–290 K. The observed phenomena can be attributed to the combined effects of forced magnetization and alteration of magnetic susceptibility during the structural phase transition that accompany the magnetic phase changes in these compounds.

The paper presents the results of the synthesis, structural studies, and investigation of the magnetic and magnetostriction properties of new multicomponent alloys based on heavy rare-earth metals ( R _1-x Y x ) 0.8 Sm 0.2 Fe 2 , where R = Tb, Gd, Dy, and Er, х = 0, 0.2, 0.4, 0.6, 0.8, and 1. It was found that alloys of these systems (except for the system with Tb) are single-phase and have the cubic С 15 Laves structure. The lattice parameters for all systems were shown to change linearly with increasing х . The main magnetic characteristics of the alloys were determined. The following practically important phenomena were found: the magnetic compensation of the sublattice magnetization, the spin reorientation, and the sign inversion of magnetostriction constants.

The structure, magnetic, magnetothermal, and magnetoelastic properties of Gd 5 Si _2-x Ge _2-x In 2 x ( x = 0–0.1) intermetallic compounds have been studied in the region of magnetostructural phase transitions. It is shown that introduction of indium creates the effect of negative pressure, leading to a change in the critical temperature of the magnetic phase transition in the monoclinic phase of the compounds studied and to partial separation of the magnetic and structural phase transitions in them.

Multicomponent alloys based on light and heavy rare-earth metals of the compositions R (Fe _1-x Al x ) 2 ( R = Pr, Nd, Tb) and Y(Fe _1-x Al x ) 2 were synthesized and their crystal structures were determined. For all these systems, the lattice parameter a of the cubic C 15 Laves phase was shown to linearly vary with increasing substitution parameter x . It was found that alloys of these systems undergo complex structural transformations caused by a change in the Al concentration in the samples.

Volumetric cubic and cylindrical samples from MQP-S Nd-Fe-B-type material were 3D-printed using the LPBF technique. Two different scanning strategies were used: the convenient single laser exposure scanning strategy and the newly proposed double scanning strategy aimed at improving the melting process and increasing the density of the synthesized material. Samples with a relative density value higher than 95% were obtained using the new scanning strategy by reducing void volume and cracks. This was achieved by decreasing internal stresses and reducing the tendency to form and propagate cracks. The double scanning strategy of half laser power followed by full power exposure provides higher magnetic properties (both coercive force and remanence). The coercive force increases with energy input decrease, while remanence has inverse dependence.

To identify promising magnetic refrigerant materials, we have studied the influence of composition variations and hydrogenation on the magnetocaloric effect (MCE) of the (Gd1-xTbx)Ni compounds. The end compositions of the series, Gd0.9Tb0.1Ni and Gd0.1Tb0.9Ni crystallize in orthorhombic CrB-type and monoclinic TbNi-type structures, respectively. Hydrogenation boosts the unit cell volume of (Gd,Tb)Ni by more than 20 % upon absorption of 4 at.H/f.u. Hydrogen absorption changes the structure type from TbNi to the CrB-type in Gd0.1Tb0.9Ni. Decrease of the Curie temperature in hydrides reaches similar to 60 K. The magnetocaloric effect in (Gd, Tb)NiHy (y = 0 and 4) obtained by indirect method in the vicinity of T-C revealed similar values of the maximum of specific isothermal entropy change Delta S-T = 20.5 J kg(-1) K-1 for Gd0.9Tb0.1Ni and its hydride Gd0.9Tb0.1NiH4 at mu 0 Delta H = 7 T. We show that the controlled synthesis of hydrides allows us to tailor the magnetocaloric effect in the multicomponent rare earth intermetallics and obtain materials with largely different T-Cs but with the same MCE values that are attractive for use in low-temperature magnetic cooling applications.

The magnetic properties of rare-earth ferrimagnetic compounds Dy 2 Fe 10 Al 7 and Ho 2 Fe 10 Al 7 with a Th 2 Zn 17 crystal structure have been studied. The temperature dependences of the magnetization and magnetocaloric effect have been examined in the temperature range of 4.2‒300 K in magnetic fields of up to 70 and 18 kOe, respectively. The temperatures of magnetic compensation of the magnetization of the rare-earth and iron sublattices have been determined. The magnetocaloric effect has been determined by the direct method. It has been found that the sign of the effect changes near the magnetic compensation point. This phenomenon has an application potential.

The influence of iron substitution by cobalt on the structural and magnetostrictive characteristics of (Tb,Ho)(Fe, Co)2-type compounds is investigated. It is established that cobalt doping of the Tb0.16Ho0.84Fe2 compound leads to an increase in the Curie temperature and a decrease in the lattice constant. It is shown that the anisotropic magnetostriction of the Tb0.16Ho0.84Fe2−xCox (x≤0.4) compounds significantly exceeds the volumetric one in the moderate (up to 1.2 T) magnetic fields. The Tb0.16Ho0.84Fe1.8Co0.2 composition with the highest saturation magnetostriction and magnetostrictive susceptibility is found.

We consider the features of the behavior of thermal expansion and magnetostriction in magnetically ordered substitutive alloys based on heavy rare earth metals, namely: TbFe2, Tb0.8Zr0.2Fe2, Tb0.8Sm0.2Fe2 and Gd0.8Sm0.2Fe2. It is found that the of thermal expansion anomalies observed in alloys are mainly due to the competition of exchange interactions. In TbFe2 and Tb0.8Zr0.2Fe2 alloys invar-type features are observed in a wide temperature range.

The effect of hydrogenation on the structure and magnetic properties of TbFe11– xCoxTi compounds with different cobalt content (x = 0, 3, 4, and 5) has been studied. An X-ray diffraction phase analysis was carried out and the parameters of the crystal structure of hydrides were determined. It is shown that hydrogenation leads to an isotropic increase in the unit cell volume. The experimental field and temperature dependence of the magnetization of single crystals hydride are studied in magnetic fields up to 90 kOe in the temperature range 5–300 K. The constants of magnetocrystalline anisotropy are determined.

The paper presents the results of the synthesis, structural studies, and investigation of the magnetic and magnetostriction properties of new multicomponent alloys based on heavy rare-earth metals (R1-xYx)(0.8)Sm0.2Fe2, where R = Tb, Gd, Dy, and Er, x = 0, 0.2, 0.4, 0.6, 0.8, and 1. It was found that alloys of these systems (except for the system with Tb) are single-phase and have the cubic.15 Laves structure. The lattice parameters for all systems were shown to change linearly with increasing.. The main magnetic characteristics of the alloys were determined. The following practically important phenomena were found: the magnetic compensation of the sublattice magnetization, the spin reorientation, and the sign inversion of magnetostriction constants.