Structure and magnetic properties of (Nd1−xErx)3Fe25Cr4.0 (0 ≤ x ≤ 0.8) compounds

The structure and magnetic properties of (Nd1-xErx)3Fe25Cr4.0 compounds with x = 0-0.8 have been investigated using x-ray powder diffraction (XRD) and magnetic measurements. It has been found that all the compounds crystallize in a Nd3(Fe,Ti)29-type structure. Substitution of Er for Nd leads to a contraction of the unit-cell volume. The Curie temperature, Tc, and the saturation magnetization, Ms, of (Nd1-xErx)3Fe25Cr4.0 decrease monotonically with increasing Er content. The easy magnetization direction (EMD) of Nd3Fe25Cr4.0 at room temperature is close to the [040] direction but may be a little out of the basal plane. With increasing Er content, the EMD changes closer to the [40-2] direction and the tilt angle increases. Both the XRD patterns and ac susceptibility indicate the appearance of a spin reorientation for x = 0-0.4 as the temperature decreases from room temperature to 77 K. The spin reorientation temperature, Tsr, increases monotonically with increasing Er content from 158 K for x = 0 to 198 K for x = 0.4. A first order magnetization process (FOMP) occurs for all the compounds, and the critical field of the FOMP decreases with increasing Er content from 6.6 T for x = 0 to 2.0 T for x = 0.7.