TbxHo0.9−xNd0.1 (Fe0.8Co0.2)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 λa, as high as 430 ppm at 3 kOe, were obtained for Tb0.25Ho0.65Nd0.1 (Fe0.8Co0.2)1.93 composite rod. The value of λa 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.
The spin configuration and spontaneous magnetostriction λ111 of TbxDy0.9−xNd0.1(Fe0.8Co0.2)1.93 (0.20 ≤ x ≤ 0.60) alloys have been investigated. The easy magnetization direction (EMD) at room temperature was observed towards the 〈111〉 axis when 0.40 ≤ x ≤ 0.60, accompanied by a rhombohedral distortion with large spontaneous magnetostriction coefficients λ111, which increases from 1640 ppm for x = 0.40 to 1900 ppm for x = 0.60. The strong 〈111〉-oriented pseudo 1–3 particulate composite was fabricated by embedding and aligning particles in a passive epoxy matrix under an applied magnetic field. An enhanced magnetostrictive effect, the large low-field magnetostriction, λa, as high as 480 ppm at 3 kOe, was obtained for the sample of x = 0.40, in an excess of 75% of its polycrystalline alloy although it only contains 27 vol. % alloy particles. This enhanced effect can be attributed to its low magnetic anisotropy, anisotropic magnetostrictive nature (e.g., λ111 ≠ λ100, 〈111〉EMD), chain structure, and the 〈111〉-textured orientation. In addition, we give a direct experimental support that the 〈111〉EMD of particle and the strong 〈111〉-textured orientation are the crucial factors to realize the enhanced magnetostrictive effect in 1–3 particulate composites.
The structural and magnetoelastic properties of (Tb 0.3 Dy 0.7 ) 1-x (Pr 0.5 Nd 0.5 ) x Fe 1.93 (0 B x B 0.20) polycrystalline alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain gauge technique. A single (Tb,Dy,Pr,Nd)Fe 2 Laves phase with a cubic MgCu 2 -type structure is formed when x B 0.12, while a small amount of impurities appear when x C 0.15. The easy magnetization direction at room temperature is detected toward \111[ axis. The analysis of XRD, magnetization and magnetostriction shows that the Pr and Nd elements joint introduction into (Tb,Dy)Fe 2 system can reduce the magnetocrystalline anisotropy and improve the magnetoelastic properties. The (Tb 0.3 Dy 0.7 ) 0.88 (Pr 0.5 Nd 0.5 ) 0.12 Fe 1.93 alloy exhibits a high low-field magnetostriction k a (*314 ppm/ 1 kOe), a large spontaneous magnetostriction coefficient k 111 (*1710 ppm), a giant saturation magnetostriction k S (*1060 ppm) and the low magnetocrystalline anisotropy at room temperature, and may make it a promising candidate for magnetostriction applications.
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