The magnetocrystalline anisotropy of R/sub 2/Co/sub 17-x/Mn/sub x/ (R=Pr, Nd, Tb, Dy and Ho) compounds

Abstract

The effect of Mn substitution on the magnetocrystalline anisotropy of R/sub 2/Co/sub 17-x/Mn/sub x/ (R=Pr, Nd, Tb, Ho and Dy) compounds have been investigated by means of X-ray diffraction (XRD) and magnetic measurements, XRD measurement on magnetically aligned samples demonstrates that for Pr (1<x<5) and Ho (2<x<4) compounds, they exhibit an easy-axis type of anisotropy at room temperature, while for Ho (x=1) compound, an easy-cone type of anisotropy, and for Nd (0<x<5) and Tb (0<x<4) compounds, an easy-plane anisotropy. The spin reorientation transitions are found in the M-T curves for Pr(1<x<5), Nd (1<x<5), Tb (2<x<4) and Ho (0<x<4) compounds. The spin-reorientation temperatures T/sub sr/ firstly decrease with Mn substitution, and then increase after x>3. The magnetic phase diagrams are given. The spin-reorientation transition might be understood as the result of the competition between the magneto-crystalline anisotropy of the R-sublattice and that of the 3d-sublattice. Room-temperature magnetocrystalline anisotropy fields HA firstly increases and then decreases with increasing Mn substitution, attaining the maximum at x=2-3. The enhancement of anisotropy is explained by preferred substitution of Mn atom in 6c Co sites. From the measurement of magnetization curve along and perpendicular to the c-axis at different temperature around the T/sub sr/, it can be implied that the spin-reorientation transitions are a continuous moment reorientation.