Magnetostriction and hysteresis of (Tb,Dy,Ho)Fe₂ alloys

The Tb/Dy ratio of Tb_0.30Dy_0.70Fe_1.95 giant magnetostrictive alloy was shifted away from 0.30/0.70 to 0.36/0.64 to enlarge the operating temperature range. However, the magnetostriction was reduced under low magnetic field and its hysteresis was enlarged with the shift of Tb/Dy ratio. Ho addition improves the magnetostriction under low magnetic field and reduces the hysteresis of Tb_xDy_yHo _zFe_1.95 (x+y+z=1). The crystal structure, lattice constant, Curie temperature, spin reorientation temperature, magnetization, magnetic anisotropy and magnetostriction of Tb_xDy_yHo _zFe_1.95 alloys were investigated. X-ray diffraction patterns demonstrate that all the samples possess MgCu₂-type cubic Laves structure. The lattice parameter, Curie temperature and magnetic anisotropy constant K₁ decreased with increasing Ho concentration. The hysteresis represented by the width of magnetostriction versus the applied field was reduced due to the addition of Ho. At a compressive stress of 10 MPa and a magnetic field of 1000Oe, the addition of Ho to the ternary Tb _xDy_yFe_1.95 compound reduced the width of magnetostriction by 25% for Tb_0.296Dy_0.472Ho _0.232Fe_1.95 and by 27% for Tb_0.296Dy _0.472Ho_0.232Fe_1.95 compared to the Tb _0.36Dy_0.64Fe_1.95 alloy, while the strains were reduced by only 3% and 9%.