Structure and magnetic properties of Nd 2(Co, Mn) 17 compounds

Abstract

X-ray diffraction (XRD) and magnetization measurements were carried out to investigate the effect of Mn substitution for Co on the structure and magnetic properties of Nd 2Co 17− x Mn x compounds with x=0–8. XRD patterns show that all samples are single phase with the rhombohedral Th 2Zn 17-type structure except the samples with x=6–8 which contain a small amount of impurity. The substitution of Mn for Co leads to a monotonic increase in unit cell volume. The saturation magnetic moment first increases slightly for x=0–2 and then decreases quickly with increasing Mn concentration. The Curie temperature T C decreases monotonously with increasing Mn content. XRD measurements on magnetically aligned samples with x=0–6 exhibit an easy-plane type of magnetocrystalline anisotropy at room temperature. For x=1–5, a spin-reorientation transition is observed above room temperature in M– T curve. This is explained by that Mn substitution for Co leads to a change of the magnetocrystalline anisotropy of the 3d-sublattice from basal plane to c-axis and to temperature-induced competition between the 3d-sublattice and Nd-sublattice anisotropy. The magnetic phase diagram is given. The magnetocrystalline anisotropy field μ 0 H A is found to decrease sharply with Mn substitution for x⩽2 and then remains nearly unchanged with increasing Mn concentration, the anisotropy constant K 1 is negative for x=1–5 with the absolute value decreases sharply.