The magnetocrystalline anisotropy of R2Co17-xMnx (R = Pr, Nd, Tb, Dy and Ho) compounds

The effect of Mn substitution on the magnetocrystaffine anisotropy of R2Co1 7-xMnx (R = Pr, Nd, Tb, Ho and Dy) compounds have been investigated by mean s 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 t emperature, 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 anisotr opy. 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. T he spin-reorientation temperatures T-sr firstly decrease with Mn substituti on, and then increase after x > 3. The magnetic phase diagrams are given. T he spin-reorientation transition might be understood as the result of the c ompetition between the magneto-crystalline anisotropy of the R-sublattice a nd that of the 3d-sublattice. Room-temperature magnetocrystalline anisotrop y fields HA firstly increases and then decreases with increasing Mn substit ution, attaining the maximum at x = 2-3. The enhancement of anisotropy is e xplained by preferred substitution of Mn atom in 6 c Co sites. From the mea surement of magnetization curve along and perpendicular to the c-axis at di fferent temperature around the T-sr, it can be implied that the spin-reorie ntation transitions are a continuous moment reorientation.