Preparation And Magnetoelastic Properties Of MgCu₂ Type Rare Earth Transition Materials

The rare-earth transition-metal compounds,Mn-doped Tb_xHo_1-xFe₂ and Co-doped Tb_0.2Dy_0.8-xPr_xFe_1.93,were prepared by high-vacuum arc-melting and subsequent annealing.The Sm_0.88Nd_0.12Fe_1.80 alloys were prepared by mechanical alloying,and the epoxy bonded 1-3 type and 0-3 type composites were fabricated by curing with and without a magnetic field.The crystal structure,curie temperature,easy magnetization direction,magnetic and magnetostrictive properties were investigated by X-ray diffraction?XRD?,vibrating sample magnetometer?VSM?,A.C.initial susceptibility tester,M?ssbauer spectra and static standard strain gauge.XRD analysis shows that 5 at%Mn-doped Tb_xHo_1-xFe₂ alloys will not effect the formation of single Laves phase.The lattice parameter a and the curie temperature T_C increase nearly linearly with increasing of Tb content,and obey the Vegard?s law.The EMD at room temperature is observed to be<100>for x?0.10,and rotates toward the<111>direction when the Tb content increases to x?0.14.The composition anisotropy compensation can be found to be near x=0.12 The XRD on magnetic-field aligned powders and M?ssbauer spectra indicate that the Mn substitution for Fe changes the spin reorientation temperature T_SR and shifts the magnetocrystalline-anisotropy compensation point to the Ho-rich side at room temperature.The minimum anisotropy is obtained for the Tb_0.12Ho_0.88Fe_1.9Mn_0.1 alloys,which has good magnetoelastic properties a high low-field magnetostriction?a³40 ppm at 2 kOe.In Tb_0.2Dy_0.8-xPr_x(Fe_0.8co_0.2)_1.93.93 alloys system,the magnetocrystalline-anisotropy compensation between Pr³⁺and Dy³⁺ions was directly verified by experiments.A small amount of Co substitution Fe can stabilize the formation of Laves phase.The solubility limit of Pr is increased to 25 at.%,and 1:3 and rare earth phase appears when further increasing Pr content for x?0.30.The easy magnetization direction rotates continuously from the<100>axis for x=0 to<110>axis,the anisotropy compensation between Pr³⁺and Dy³⁺is realized at room temperature.Sm_0.88Nd_0.12Fe_1.80.80 compounds were synthesized by mechanical alloying?MA?and subsequent annealing process.The phase and magnetostrictive properties of the alloys at the different annealing temperatures were investigated.XRD analysis shows that the single Laves phase can be frabicated when annealing temperature at 650°C.With increasing of the annealing temperature,the magnetostrictive properties of the alloys will increased,and the linear anisotropic magnetostriction?_a is 1100 ppm at 12 kOe magnetic field.Furthermore,the 1-3 type composite with 30 vol.%has a better magnetostrictive performance than that of the 0-3 type composite.It is noted that a large linear anisotropic magnetostriction?a of-758 ppm is detected for the 1-3 type composite which is appropriately 69%of its alloy value at the 12 kOe magnetic field.