Magnetic and structural properties of TbFe 10.8-xCo xW 1.2 alloys

Abstract

A series of new alloys of composition TbFe 10.5Co ξW 1.2(0⩽ x ⩽10.8) has been synthesized and studied for their hard magnetic properties over the temperature range 4.2–1200 K. It is found that all compounds with x ⩽ 5 crystallize in a tetragonal structure of the ThMn 19 type. At higher cobalt content, i.e. x ⩽ 5, a considerable amount of an extraneous phase of the rhombohedral Th 2Zn 27 structure is observed. These compounds exhibit planar anisotropy for ξ ⩽ 5 at room temperature. Above room temperature the plane-tocone-type spin reorientation is found for this system. The Curie temperature T c of these materials is considerably enhanced by cobalt substitution and ranges from 560 K (TbFe 0.8W 1.2) to 1003 K (TbFe 5.8Co 5W 1.2). The effect of cobalt substitution on the anisotropic behaviour in the Tb (Fe, Co) 10.8W 1.2system is analysed.