Influence on magnetic properties of substitution of Co for Fe in TbFe 11.3Nb 0.7

Abstract

The magnetic properties of Tb(Fe 1− x Co x ) 11.3Nb 0.7 compounds with x=0, 0.05, 0.1, 0.15, 0.2 and 0.3 have been investigated. All compounds studied crystallize in the ThMn 12-type of structure. Substitution of Co for Fe leads to a contraction of the unit-cell volume. The Curie temperature clearly increases with increasing Co content from 551 K for x=0 to 831 K for x=0.3. The magnetic moment of the transition-metal sublattice increases with increasing Co content from 22.2 μ B/f.u. for x=0 to 23.1 μ B/f.u. for x=0.3. As the temperature increases, a spin reorientation from easy-plane to easy-cone is found in all compounds investigated. The spin-reorientation temperatures T sr have been derived from the temperature dependence of the magnetization in a low field and decrease monotonously with increasing Co content. The easy magnetization direction at room temperature has been determined by X-ray diffraction on magnetically-aligned powder samples. The influence of the substitution of Co for Fe on the magnetic anisotropy is discussed in terms of crystal-field theory.