Ye.V. Belozerov

Magnetic properties and crystal structure of novel high anisotropic compounds based on the RFeV system (RY, Nd, Sm, Gd)

Abstract We have investigated the crystal structure and magnetic properties of novel ternary compounds of the composition R 2 (Fe 0.91 V 0.09 ) 17 (R≡Y, Nd, Sm, Gd). X-ray diffraction showed that their crystal structure is a superstructure of a new type based on the CaCu 6 structure, but with lattice parameters five times larger than those of CaCu 5 . The Curie temperature and saturation magnetization of the compounds studied fall into the ranges 440–520 K and 15–30 μ B (f.u.) −1 at 4.2 K respectively. The influence of dissolved cobalt, carbon and nitrogen on the magnetic properties of the compounds R 2 (Fe 0.91 V 0.09 ) 17 has been studied.

The structure and magnetic properties of rapidly quenched and annealed multi-phase nanocrystalline Nd9Fe91−xBx ribbons

Abstract Melt-spun and annealed Nd 9 Fe 91− x B x ribbons with 0 ≤ x ≤ 9 have been studied by means of X-ray diffraction, thermomagnetic analysis and magnetic measurements. The metastable phase diagram up to 780°C has been plotted. A metastable phase of the TbCu 2 structure has been identified in the ribbons of binary composition and those containing up to 7 at.% B. The Curie temperature of this phase was found to be strongly affected by both boron content and annealing temperature. The structure of exchange coupled nanocrystallines of Nd 2 Fe 14 B. α-Fe and Fe 3 B was realized by means of short-time annealing. The annealed isotropic Nd 9 Fe 84 B, ribbons had a remanence of 100.5 emu g −1 , an intrinsic coercivity of 4.5 kOe, and an energy product of about 13 MG Oe. The details of structure formation, as well as the criteria and conditions for the effective exchange coupling, are discussed.

Mechanisms controlling magnetic properties of pseudobinary compounds TbNi5−xMx (M=Cu or Al)

Abstract Magnetic properties and heat capacity of the pseudobinary TbNi 5− x Cu x and TbNi 5− x Al x alloys have been studied for x ⩽2.5 and x ⩽1.5, respectively. The substitution of Cu or Al for Ni decreases sharply the spontaneous magnetic moment, increases the magnetic anisotropy in the “easy” basal plane, and leads to strong magnetic domain wall pinning. The Curie temperature T C in TbNi 5− x Cu x depends on x non-monotonously and has a maximum value at x =1, while T C in TbNi 5− x Al x does not depend on composition up to x =1 and sharply decreases at x >1. These results are explained by the effects of random local crystal fields, band magnetism and heterogeneous polarization of the mixed 3d band.

Investigation of phase composition and remanence enhancement in rapidly quenched Nd9(Fe, Co)85B6 alloys

Melt-spun and annealed Nd9(Fe1−xCox)85B6 alloys with x = 0–0.4 have been studied by means of X-ray diffraction, transmission electron microscopy, thermomagnetic analysis and magnetic measurements. Both quenching of the alloys and crystallization of the amorphous phase are accompanied by the formation of a metastable phase of ThCu7 type. When 0 ⩽ x ⩽ 0.3, short-time annealing at about 680°C results in coexistence of nanocrystalline exchange coupled Nd2(Fe,Co)14B and b.c.c. FeCo phases. Because of the stabilizing effect of Co on the 1:7 phase, the annealing that is optimal with respect to the sizes of the α grains is found to be insufficient for complete disappearance of the 1:7 phase in Co substituted alloys.

Magnetocrystalline anisotropy and exchange interactions in the novel R3(Fe, V)29 compounds (R Y, Nd, Sm)

A type of magnetocrystalline anisotropy and exchange interactions of the novel ternary R3(Fe, V)29 compounds (R  Y, Nd, Sm) have been investigated. The compounds are uniaxial ferromagnets with easy magnetization direction along the [2 0 1] axis of the monoclinic lattice at room temperature. The temperature variations of the magnetic moment and the first anisotropy constant for Y3(Fe, V)29 are presented. The first order magnetization process along the hard magnetization direction takes place for Sm3(Fe, V)29 at T < 120 K. A magnetic anomaly is detected in the temperature dependence of the a.c. susceptibility for Nd3(Fe, V)29 which can be related to a spin reorientation.

The formation of Z-phase Sm(Fe,Ti)8.5

Abstract The high-temperature modification Sm 2 (Fe,Ti) 17 of Th 2 Ni 17 type was found to exist in the Sm(Fe 1− x ti x ) y alloy system (0.04⩽ x ⩽0.07 and 8.0⩽ y ⩽9.0) at T ⩾1250 °C. More low-temperature phases Sm(Fe,Ti) 12 and Sm 2 (Fe,Ti) 17 of Th 2 Zn 17 type form from this modification. A ternary Sm(Fe 0.935 Ti 0.065 ) 8.5 compound analogous to the Z-phase Sm(Fe 0.91 V 0.09 ) 8.5 is obtained in the interval 1150–1250 °C. It can be considered to have a new type of a superstructure based on the CaCu 5 -type structure with a monoclinic unit cell having parameters a =0.972 nm, b =0.856 nm, c =1.063 nm, β=96° 50′.

New phases in Tb–Fe–Si system

Abstract The phase composition of the Tb(Fe 1− x Si x ) y alloys, where x =0.09 or 0.15 and y =8.5 or 9.667, has been studied by X-ray diffraction using micromonocrystals. Reflections of the Tb 3 (Fe,Si) 29 phase and of two new previously unknown phases are found. Models of the atomic arrangement in the new phases correlating well with the experimental diffraction patterns are suggested. Both new phases can be formed by the dumb-bell substitution for Tb atoms in the CaCu 5 lattice. According to the models, the compositions of phases are Tb 12 (Fe,Si) 109 and Tb 4 (Fe,Si) 41 .

Peculiarities of the R3(Fe,Si)29 phase formation in the SmFeSi system

Abstract The phase content of the Sm(Fe 1− x Si x ) y alloys (0.05≤ x ≤0.15; 8.5≤ y ≤12) has been studied by X-ray diffraction using micromonocrystals. The compounds Sm 2 (Fe,Si) 17 , Sm(Fe,Si) 12 and a novel Sm 3 (Fe,Si) 29 compound with a monoclinic unit cell are found. The lattice parameters of Sm 3 (Fe,Si) 29 are: a =1.056 nm, b =0.850 nm, c =0.966 nm, β =96.8°. This compound forms as a result of a solid state transformation from the high-temperature Sm 2 (Fe,Si) 17 phase. Diffuse effects observed in rocking photographs suggest transition structures arising from this transformation. The Curie temperatures of Sm 3 (Fe,Si) 29 vary in the interval 496–521 K.

Crystal Structure and Magnetic Properties of Novel Compound PrFe8Ga3C

We have synthesized a novel intermetallic compound PrFe8Ga3C and studied its structure and magnetic properties. X-ray diffraction analysis revealed that the compound possesses a tetragonal BaCd11-type structure (space group I41/amd). In this structure Ga atoms occupy the same sites as Fe atoms with preferably filling the 4(b) site. Magnetization curves have been measured on the aligned powder samples. Below the Curie temperature TC = 400 K the easy magnetization direction was found to orient within the (100) plane. At 80 K the compound has a spontaneous magnetization of 97 emu/g and anisotropy constant of 4.2107 erg/cm3. At room temperature these values reduce to 78 emu/g and 4.7106 erg/cm3, respectively.

Intermetallic compounds in the iron-rich SmFeRe alloys

In the iron-rich SmFeRe alloys, novel ternary compounds Sm(Fe,Re)12 of the ThMn12 type and Sm3(Fe,Re)24 with a monoclinic unit cell have been discovered. Both of these compounds are highly anisotropic uniaxial ferromagnets with the anisotropy fields more than 8 MA m−1. The Curie temperatures and saturation magnetization at 4.2 K are equal to 415 K and 92 A m2kg−1 respectivelt for Sm(Fe1−xRex−2)12 and 391 K and 109 A m2kg−1 for Sm3(Fe0.92Re0.09)29. The concentration dependences of the lattice parameters. Curie temperature and saturation magnetization for the substituted Sm2(Fe1−xRex)17 compounds (x ⪕ 0.14) are presented.