Magnetic Properties And Thermal Expansion Anomaly Of R₂Al(Fe, Mn)₁₆ (R=Nd, Er) Compounds

The structural, magnetic properties and thermal expansion behaviors of Nd₂AlFe_16-xMn_x(x=1,2,3,4,5) and Er₂AlFe_16-xMn_x (x=1,2,3,4,6,8) compounds have been studied by means of X-Ray diffraction and magnetization measurements. The effect of Mn substitution on the structure parameter, magnetic properties and thermal expansion behaviors of Nd₂AlFe_16-xMn_x and Er₂AlFe_16-xMn_x compounds are analyzed, and spontaneous magnetostriction of Nd₂AlFe_16-xMn_x and Er₂AlFe_16-xMn_x compounds is also discussed. The Gd₂Fe₁₇ compounds with Th₂Zn₁₇-type structure and Th₂Ni₁₇-type structure were formed by arc melting. Both of them are studied by means of X-Ray diffraction and magnetization measurements.The results show that there are anisotropic strong and positive spontaneous magnetostrictions in the compounds Nd₂AlFe_16-xMn_x and Er₂AlFe_16-xMn_x. The substitution of atom Mn leads to rapid drop in spontaneous magnetization and Curie temperature, and it also influences magnetic anisotropy. When the magnetic anisotropy appears from in plane to along axis, the spontaneous magnetostriction will increase. In temperature range 282-342K, the Nd₂AlFe₁₅Mn compound possesses good Invar property. Because the expansion coefficient is about 10^-6, which is much the same as the Invar alloys used widely, the Nd₂AlFe₁₅Mn compound has promising future. The magnetic moments of Gd-sublattice and Fe-sublattice in Gd₂Fe₁₇ compound from 77 to 500K were measured by this way with a vibrating sample magnetometer. The slightly difference between Curie temperatures T_c of the two-structure samples indicates that R-T interaction is much weaker than T-T interaction.