Synthesis and Magnetic Properties of Gd₃ (Fe, Co,Cr)₂₉ Compounds

Formation and magnetic properties of the Gd₃Fe_29-x-yCo_xCr_y compounds have been investigated. It has been found that formation of single phase compounds Gd₃Fe_29-x-yCo_xCr_y with Nd₃(Fe,Ti)₂₉-type structure depends strongly on the content of stabilizing element Cr, and the solid-solution limit of Co in Gd₃Fe_29-x-yCo_xCr_y compounds increases with Cr content. Pure Co-based Gd₃Co_29-yCr_y compounds with Nd₃(Fe,Ti)₂₉-type structure have been successfully synthesized with y = 6.5 and 7.0. The Curie temperature T_c of Gd₃Fe_29-x-yCo_xCr_y compounds increases with increasing Co content x at fixed y, whereas increase of the Cr content leads to an obvious decrease of T_c of the Gd₃Co_29-yCr_y compounds. Composition dependence of the saturation magnetization at 5 K reaches a maximum around x =7.5 and y = 4. It is worth noting that substitution of Co for Fe results in a significant change of magnetocrystalline anisotropy of the Gd₃Fe_29-x-yCo_xCr_y compounds and changes the easy magnetization direction from basal-plane to easy-axis when x > 10 and y = 4.