Magnetic behaviour of YFe 10.8 − xCo xT 1.2 systems ( T ≡ W and Re)

Abstract

The results of magnetic (saturation magnetization, Curie temperature, and anisotropy field) and structural measurements performed on YFe 10.8 − x Co x T 1.2 compounds ( T ≡ W and Re and 0 ⩽ x ⩽ 10.8) are presented. All alloys with x ⩽ 7.8 crystallize in a tetragonal structure of the ThMn 12 type. The lattice parameters decrease monotonically with the increasing cobalt concentration. A characteristic maximum in composition dependence of the saturation magnetization is found for ≈2. YFe 10.8T 1.2 ( T ≡ W or Re) have an average iron moment of 1.8 μ B , at 77 K. A partial replacement of iron by cobalt in the YFe 10.8T 1.2 system ( T ≡ W or Re) leads to an increase in the Curie temperature. These compounds exhibit uniaxial anisotropy for x ⩽ 2, at room temperature. For higher cobalt content the anisotropy becomes planar. The magnetic anisotropy ( H A ) is found to increase with decreasing temperature. For example, H A for the YFe 10.8Re 1.2 alloy is 25 kOe and 40 kOe, at 295 K and 77 K respectively. A comparison with the YFe 10− x Co x V 2 system is also presented.