Magnetoelastic properties of epoxy resin based Tb_xHo_0.9−xNd_0.1 (Fe_0.8Co_0.2)_1.93 particulate composites

Tb_xHo_0.9−xNd_0.1 (Fe_0.8Co_0.2)_1.93 (0 ⩽ x ⩽ 0.40) particulate composites were prepared by embedding and aligning alloy particles in an epoxy matrix with and without a magnetic curing field. The magnetoelastic properties were investigated as functions of composition, particle volume fraction and macroscopic structure of the composite. The magnetic anisotropy compensation point was found to be around x = 0.25, where the easy magnetization direction (EMD) at room temperature was detected lying along ⟨ 1 1 1 ⟩ axis. The composite with ⟨ 1 1 1 ⟩ preferred orientation and pseudo-1-3 type structure was prepared under an applied magnetic field of 12 kOe. An enhanced magnetoelastic effect and large low-field magnetostriction λ_a, as high as 430 ppm at 3 kOe, were obtained for Tb_0.25Ho_0.65Nd_0.1 (Fe_0.8Co_0.2)_1.93 composite rod. The value of λ_a was of 72 % of its polycrystalline alloy (~595 ppm/3 kOe) although it only contained 30 vol.% of the alloy particles. This enhanced effect can be attributed to the larger λ₁₁₁ (as compared to λ₁₀₀), low magnetic anisotropy, easy magnetization direction (EMD) along the ⟨ 1 1 1 ⟩ axis and ⟨ 1 1 1 ⟩-textured orientation of the alloy particles as well as the chain-like structure of the composite. The good magnetoelastic properties of the composite, in spite of the fact that it contained only 30 vol.% of the alloy particles with light rare-earth Nd element in the insulating epoxy, would make it a potential material for magnetostriction application.