Study On Magnetization Mechanism And Magnetostrictive Effect Of RFe₂ Compounds

RFe₂-type rare-earth transition-metal compounds have large magnetostrictive value and rich magnetic properties.In this paper,Tbx Ho1-x Fe1.9Mn0.1 and light-rare-earth Nd-doped Tbx Ho0.9-xNd0.1Fe1.8Mn0.1 compounds were prepared by arc melting and annealing.Test methods such as Xray diffraction(XRD),Lorentz transmission electron microscope(LTEM),electron holography(EH),vibrating sample magnetometer(VSM),superconducting quantum interferometer(SQUID)and standard strain gauge techniques were used.The structure,magnetic properties,magnetic domain structure,magnetocrystalline anisotropy,easy magnetization direction(EMD)and magnetostrictive properties of magnetostrictive alloys were studied.Tbx Ho1-x Fe1.9Mn0.1(0.08 ? x ? 0.16)alloy system,using LTEM to characterize the magnetic domain structure.The experiment of EH technology directly verified the change rule of EMD with the composition.When x ? 0.10,EMD is <100> axis,and when x ? 0.12,EMD is <111> axis.Based on the changes in EMD and by evaluating the magnetocrystalline anisotropy constant K1,magnetic properties and magnetostrictive properties,it is determined that when the composition is about x = 0.12,the alloy achieves magnetocrystalline anisotropy compensation.According to the experiment of the magnetic domain wall movement by the in-situ magnetic field LTEM,shows that when the composition is on the Tb-rich side x = 0.16,the critical magnetic field Hcr is 100 Oe,and as the Tb content decreases,the Hcr continuously decreases to 60 Oe(x = 0.12).Tb0.12Ho0.88Fe1.9Mn0.1 alloy achieves large low-field magnetostriction,and ?_a is 200 ppm when H= 1 kOe,which is a good magnetostrictive material.This work helps to understand the relationship between magnetocrystalline anisotropy,magnetization process,magnetic domain wall motion and magnetostriction in the C15 Laves phase system.For the Tbx Ho0.9-x Nd0.1Fe1.8Mn0.1(0.08 ? x ? 0.25)alloy system,the effect of the introduction of light-rare-earth Nd on the phase structure and magnetostrictive properties was studied.Experiments show that the EMD of the alloy composition at x ? 0.08 is the <100> axis,and when x ? 0.15,the EMD is the <111> axis.EH technology further confirms the change of EMD with the composition.In addition,the relationship between the magnetic domain structure,the difficulty of domain wall movement,and the magnetocrystalline anisotropy was studied by the in-situ magnetic field LTEM.When x = 0.15,it is near the magnetocrystalline anisotropy compensation point.Tb0.15Ho0.75Nd0.1Fe1.8Mn0.1 alloy has a large low-field magnetostriction value,?_a is 322 ppm at 2kOe.This work can further deepen the understanding of the relationship between magnetocrystalline anisotropy,composition compensation,domain wall motion of rare earth giant magnetostrictive materials doped with light-rare-earth.