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Single crystals of an orthorhombic compound FeB have been synthesized. Based on the data of magnetic measurements and X-ray diffraction analysis, it has been shown that two mutually perpendicular preferred magnetization axes exist in the orthorhombic single crystals of FeB: the easy axis (EA) corresponds to the crystallographic axis [010], and the hard axis (HA), to the [100] axis. The function of the energy of magnetocrystalline anisotropy (MCA) of the orthorhombic magnets has been analyzed for extrema. Orientations of the EAs and HAs have been determined. It has been established that in the orthorhombic magnets there is always realized a single type of MCA: two preferred mutually perpendicular axes always exist in the crystals, one of which is an EA, and the other is an HA. Expressions for the anisotropy fields of orthorhombic magnets have been obtained. The constants of MCA of the orthorhombic compound FeB have been calculated to be K1* ≈ 4 × 105 J/m3 and K2* 7×104 J/m3. The domain structure on the planes (100), (010), and (001) of the FeB single crystals has been studied. It has been shown that the main volume of the sample is occupied by stripe domains ∼40 μm wide with the walls oriented along (100) crystallographic planes. It has been found that the structure of closure domains on the plane (010) of the FeB single crystals has some specific features, namely, there exists a preferred direction in the structure for the orientation of the boundaries of the main domains, and the closure domains have the shape of regular rhombs. A model of the domain structure of FeB single crystals is suggested.

A study on the magnetocaloric effect (MCE) has been carried out on the HoCo 5 single crystal using a direct method in the temperature range 78–300 K and in a magnetic field of 1.3 T at various orientations of the single crystal with respect to the direction of external magnetic field. Our research has shown that magnetic anisotropy strongly affects magnitude and sign of the MCE in the regions of spin-reorientation phase transitions. In addition, the magnetic domain structure of the HoCo 5 single crystal in (0 0 1) plane in the temperature range from room temperature down to 4.2 K was investigated.

The magnetic domain structure on (1 0 0), (1 1 0), (0 0 1) and arbitrary oriented planes of the R(FeCo) 11 Ti single crystals (R = Dy, Tb) is investigated. The role of the stress-induced magnetic anisotropy in the DS formation and the spin-reorientation transitions is analyzed. It is shown that the magnetoelastic contribution to the anisotropy in these compounds is large and can cause changes of the spin-reorientation temperatures and special domain patterns formation.

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.

In ternary R 3 Fe 33 - x Ti 3 ( x = 0 , 1 , … , 7 , R = Gd , Y ) and R 3 Fe 33 - x Ti 3 ( R = Tb , Ho , Dy , Er , x = 0 , 3 , 6 , 9 ) alloys, the anomalous wide homogeneous region of ThMn12 structure has been obtained. The single-crystal samples for each composition R3Fe33−xTi3 were prepared. By means of thermomagnetic analysis, it is shown that the TC of these single crystals monotonically decreases with the decrease in Fe concentration. With the decrease of iron concentration, the magnitude of magnetization saturation steadily decreases too. On the other hand, the temperatures of spin reorientation phases transition TSR for R = Tb , Ho , Dy , Er increase. From this, it follows that by the small changes in the Fe concentration it is possible to make a significant change of parameters of exchange interaction between R and 3d sublattices.

The tetragonal ThMn 12 -type, single crystalline DyFe 10 CoTi sample has been investigated by torque and magnetization measurements and observation of domain structure at various temperatures between 10–300 K and in magnetic field from B =0 to 0.15 T. These examinations showed that the magnetic structure of DyFe 10 CoTi changes from “easy axis” ( c -axis) type to conical at 225 K and to “easy plane” ( ab plane) type at 100 K.

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.

The effect of the substitution of Co for Fe on the magnetic anisotropy in YTiFe11−xCox (0≤x≤5) single crystals has been studied by using torque and vibrating-sample magnetometry techniques. The K1 and K2 values were calculated. The Co ion gives a resultant anisotropy which is opposite to that of Fe. A competition is expected to take place in the composition range 5

The aim of this work is to study the influence of substitution of Co for Fe on the magnetocrystalline anisotropy and spin reorientation transition in TbFe 11− x Co x Ti ( x =0;0.5;1;2;3;4;5) compounds. The anisotropy study has been performed by means of torque and magnetization measurements on single crystal samples. It was shown that increase of the Co content in Tb(FeCo) 11 Ti compounds leads to an increase of the Curie temperatures T c . The temperature of the magnetic phase transition during which the easy magnetic direction (EMD) changes from the c-axis via a cone to the basal plane has been found to decrease with increasing Co concentration. On the basis of the experimental results a T − x magnetic phase diagram was constructed. The appearance of phase transitions can be explained by the temperature-dependent competition between the planar Tb sublattice anisotropy and the transition metal (FeCo) 11 sublattice anisotropy.

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.

Crystallographic structure, domain structure and magnetic properties of ternary Gd 3 Fe x Ti 3 ( x =34, 33, …, 24), TbFe 11 Ti and TbFe 10 Ti alloys and single crystals are investigated. It is shown that all these compounds have a ThMn 12 tetragonal crystal structure. The wide homogeneous region for the ThMn 12 structure detected for this group of compounds is used to explain the differences in the values of spin-reorientation temperatures of RFe 11 Ti compounds found by different authors.

The magnetization reversal behaviour of individual grains was studied by direct domain structure observations. On this basis the angular dependence of the saturation field Hs, critical field of reverse domain removal, Hk, and nucleation field Hn was found to obey the law 1/cos(ϕ − ϕm), where ϕm is the angle between the grain easy axis and the axis of magnet texture.