Structural, magnetic and magnetostrictive properties of Co-doped Tb1-xHoxFe2 (0 ≤ x ≤ 1.0) alloys

Abstract

Structural, magnetic, and magnetostrictive properties of Tb1-xHox(Fe0.8Co0.2)2 (0 ≤ x ≤ 1.0) alloys have been investigated by means of x-ray diffraction, ac initial susceptibility, an alternating gradient magnetometer and a standard strain gauge technique. A single (Tb,Ho)(Fe,Co)2 Laves phase with a cubic MgCu2-type structure is formed when 0.50 ≤ x ≤ 1.0, while the secondary phase with a PuNi3-type structure occurs at higher Tb content for 0 ≤ x ≤ 0.40. The easy direction of magnetization (EMD) is observed toward 〈111〉 when 0 ≤ x ≤ 0.75, accompanied by a rhombohedral distortion with large spontaneous magnetostriction coefficients λ111. The abnormal λ100 of –550 ppm for x = 0 and as larger than 300 ppm for 0.60 ≤ x ≤ 0.75 were observed, which can be ascribed to the filling of the 3d band due to Co substitution for Fe. The 20 at.% Co substitution for Fe moves the anisotropy compensation point to the Tb-rich side, and increases the Curie temperature TC with about 30 K as compared to the Co-free Tb1-xHoxFe2 alloys. The Tb0.25Ho0.75(Fe0.8Co0.2)2 alloy has a large magnetostriction at a relatively low magnetic field and a low anisotropy accompanied by the minimum coercivity, and may make it a promising magnetostrictive material.