M.I. Bartashevich

Magnetic and magnetoelastic properties of DyFe11Ti single crystals

Abstract The magnetic properties and thermal expansion of the single crystals of DyFe11Ti are investigated in the temperature range 4.2–800 K. Besides of the magnetic ordering at T = 550 K and spin reorientation of the “cone-axis” type at T = 220 K, another phase transition was found at T = 120 K. It is apparently connected with a noncollinearity of the Dy sublattice at low temperatures. The magnetic ordering and the spin reorientation are accompanied by large magnetostrictive deformations.

Ferromagnetism in the UCo1-xRuxAl quasiternary intermetallics

Abstract We report the structure and magnetic investigations of the quasiternary UCo1-xRuxAl compounds crystallizing in the hexagonal structure of the ZrNiAl type. A large deviation from linearity is observed in the concentration dependence of lattice parameters, positive for a and negative for c, whereas the unit-cell volume V obeys Vegards law satisfactorily. The nonlinearity is explained by a preferential occupation by the Co and Ru atoms of the two non-equivalent positions of the transition metal in the lattice. Although UCoAl and URuAl are paramagnetic down to low temperatures, ferromagnetism is observed in a wide concentration range of quasiternary solid solutions UCo1-xRuxAl. Both the Curie temperature and the spontaneous magnetization reach their maximum values of 60 K and 0.6μB (formula unit)−1 respectively in UCo0.7Ru0.3Al. The samples in the Ru concentration range 0.5 ≤ x ≤ 0.7 exhibit a second phase transition in the ordered state, indicated by anomalies in temperature dependence of both the ...

Magnetic anisotropy and magnetostriction of UFe10Si2

Abstract The magnetic anisotropy and magnetostriction of UFe10Si2 were studied on aligned polycrystals. At 4.2 K the magnetic anisotropy is described by K1 = 3.0 MJ m−3 and K2 = −0.9 MJ m−3. The magnetostriction constants obtained from the magnetostriction and thermal expansion measurements are λ1α,0 = 2.14×10−3, λ2α,0 = 6.07×10−3, λ1α,2 = −0.4×10−4, λ2α,2 = 0.9×10−4and λγ,2 = 1.8×10−4.

Magnetostriction of UNiGa at metamagnetic transition

Abstract Longitudinal and transverse magnetostrictions of the antiferromagnetic compound UNiGa were measured at 4.2 K on a single crystal in a magnetic field applied along the c axis. The metamagnetic transition in the vicinity of 1 T field causes a contraction of the crystal along the c axis by 2.1×10−4 and an expansion along the a axis by 1.0×10−4, with negligible volume effect owing to cancellation of the linear strains. The magnetostriction has a large field hysteresis. The width of the hysteresis depends strongly on the rate of field variation, ranging from 0.3 T in a steady field to 1.4 T for d B d t = 3 T ms −1 , indicating a large magnetic viscosity of the compound.

Magnetic properties and thermal expansion of R2Fe14BH3.4 (R = Y, Gd) single crystals

Abstract The change in the magnetic and crystallographic properties was studied in single crystals of hydrides R2Fe14BH3.4 (R = Y, Gd). The absorption of hydrogen leads to an anisotropic expansion of the crystal lattice, a great change of thermal expansion coefficients, increasing of Curie temperature and Fe-ion magnetic moments and weakening of Gd-Fe exchange interaction. The hydrogen significantly reduces the uniaxial anisotropy of Fe-sublattice unlike the plane anisotropy of Gd-sublattice, which results in the appearance of a spin-reorientation phase transition in the hydride with Gd.

Magnetic properties of Tb1-xYxMn6Sn6 compounds

Abstract The magnetic properties of Tb 1− x Y x Mn 6 Sn 6 compounds (0≤ x ≤1) have been studied in high magnetic fields up to 40 T. The compounds for x ≤0.6 are found to be ferrimagnets, while for x ≥0.9 they are antiferromagnets. The Curie and spin-reorientation temperatures of the ferrimagnets gradually decrease with increasing x . First-order magnetization processes are observed for the compounds with x ≤0.2. For the antiferromagnetic YMn 6 Sn 6 and Tb 0.1 Y 0.9 Mn 6 Sn 6 compounds, metamagnetic transitions are observed. Using susceptibility measurements we plotted the concentration magnetic phase diagram of the system. The effect of pressure on the magnetization curve of Tb 0.1 Y 0.9 Mn 6 Sn 6 was studied at 4.2 K. The critical field of the metamagnetic transition decreases from 1.6 down to 1.0 T with increasing pressure up to 1.2 GPa.

Magnetic properties of Mn3(Ga, Al)C under high magnetic field and high pressure

Abstract Mn 3 GaC is antiferromagnetic (AFM) at low temperatures and ferromagnetic (FM) above T t ( ∼ 160K). The magnetization of Mn 3 Ga 1− x Al x C with x ⩽ 0.08 has been measured under pressure ( p ) with a special interest in the p dependence of magnetic properties in this system. It is found that the pressure enhances the magnetic moment of Mn μ FM in the FM phase and changes the AFM to a new magnetic phase with spontaneous magnetization. The forced magnetostriction of Mn 3 Ga 1− x Al x C with x = 0.015 and 0.07 indicates μ FM NEW PHASE AFM .

Magnetic anisotropy of UCo10Si2

Abstract Magnetic properties of UCo 10 Si 2 have been studied on aligned powders. Results are compared with properties of the isostructural compound YCo 10 Si 2 . The Curie temperature ( T C = 550K) and the molecular magnetic moment (μ m = 8.6 μ B ) were found to be considerably lower in the U compound compared with YCo 10 Si 2 (750 K and 11.0 μ B respectively). However, UCo 10 Si 2 has a strong uniaxial magnetic anisotropy (the first anistrophy constant K 1 = 3.3MJ m −3 at 4.2 K), whereas YCo 10 Si 2 has anisotrophy of the cone type. If the difference in anisotropy is attributed to the U sublattice, this might point to a magnetic state of U in UCo 10 Si 2 like in the Fe isostructural analogue UFe 10 Si 2 .

Magnetic properties of (Y1 − xThx)2Fe14B

Abstract The concentration and temperature dependencies of magnetic anisotropy in the quasiternary (Y 1 − x Th x ) 2 Fe 14 B system have been studied on aligned powders. With increasing Th content, the enhancement of the uniaxial anisotropy at low temperatures ( K 1 at 4.2 K increases from 0.8 MJ m −3 for × = 0 to 1.5 MJ m −3 for × = 1) and the change in K 1 ( T ) behaviour from anomalous characteristic for Y 2 Fe 14 B to the monotonous decrease with increasing temperature have been found.

High-field magnetization process in Mn1.9Cr0.1Sb

The compound Mn1.9Cr0.1Sb shows a first-order transition from the ferrimagnetic (FI) to the antiferromagnetic (AF) state at T1 = 265 K with decreasing temperature. High magnetic fields (up to 60 T) produce AF-FI transitions below Tt. The temperature dependence of the critical field is nonlinear and shows T2 character at low temperatures (T < 150 K), in contrast to the exchange inversion model of Kittel. This behavior is connected with the itinerant magnetism of 3d-electrons of Mn atoms resulting in a large electronic contribution to the change in free energy at the field-induced first-order AF-FI transition. The field-induced phase transition from the AF to the FI state is accompanied by an increase in the electronic specific heat coefficient γ by 13 mJ K−2 mol−1 as estimated from the magnetization measurements using thermodynamic relation.