Bonded Magnetostrictive Materials Of Sm <sub> Ix </ Sub> R <sub> X </ Sub> Fe <sub> 2 </ Sub> (r = Er, Dy) Preparation And Performance Study

The epoxy bonded SmFe₂ and Sm_1-xR_xFe₂(R=Er, Dy) compounds were prepared. The matrix of bonded SmFe₂ compound is a MgCu₂ structure. The structure and the size of their powder were investigated by X-ray diffraction meter. The Curie temperatures and the M-T curves of the samples are measured on an vibrating sample magnetometer (VSM). The main experimental results and two sublattice molecular field analysis are as follows.(1) The dependence of the magnetostriction of epoxy bonded SmFe₂ and Sm_1-xEr_xFe₂ (x=0.1, 0.3, 0.4, 0.7) on model pressure and particle size were studied. The optimum prepared condition of bonded SmFe₂ is the epoxy content is in the range of 3%-4% and the model pressure is 90 MPa, particle size is 120 μm. It has been found that the magnetostriction of Sm_0.9Er_0.1Fe₂ is a little larger than SmFe₂ at low field. The reason is that magnetocrystalline anisotropy constant decreases when Er doped into SmFe₂ matrix. The magnetostriction of bonded SmFe₂ is -319 ppm and Sm_0.9Er_0.1Fe₂ is -340 ppm at a field of 0.7 T .respectively.(2) In order to get better magnetostriction, the bonded Sm_0.88Dy_0.12Fe₂ was prepared and the dependence of magnetostriction on particle size, model pressure and magnetic orientation were studied. Mixed the epoxy with the powder in the proportion of 3 to 100, when particle size reaches 120μm, the magnetostriction is optimum. The magnetostriction of bonded Sm_0.88Py_0.12Fe₂ increases with the increasing model pressure up to 98 MPa , then decreases. With the increase of magnetic orientation, the magnetostricion becomes a little better. The magnetostriction of bonded Sm_0.88Dy_0.12Fe₂ reaches -450 ppm at a field of 0.7 T. It indicates that bonded Sm_0.88Dy_0.12Fe₂ is optimum candidate for application.(3) Two-sublattice molecular field theory analysis can describe the temperature dependence of magnetization of doped rare earth into RFe₂ matrix. The temperature dependence of magnetization of Sm_1-xEr_xFe₂(x=0.1, 0.3, 0.4, 0.7) intermetallic compounds molecular field theory (MFT) were studied and the results were very consistent with the experimental data, so was the obtained Curie temperatures. The exchange couplingconstants and exchange energies α_FeFe,α_FeR,α_RR were caculated, too. α_FeFe dominates the three kinds of interaction, implying that the magnetic interaction is dominated by the...