Phase stability, crystal structure, and magnetic properties of NdCo 7−xHf x compounds

Abstract

The phase stability, crystal structure, and magnetic properties of NdCo 7− x Hf x ( x = 0.1 , 0.2, 0.3) compounds were studied by means of X-ray powder diffraction and magnetic measurements. A minor impurity phase coexists with the main 1:7 phase in the as-cast compound NdCo 7− x Hf x with x = 0.1 and 0.3. The compound with x = 0.2 crystallizes in the TbCu 7-type structure with the space group P6/mmm. According to the structure refinement, the doping element Hf prefers to occupy the 2e site. The phase stability of NdCo 6.8Hf 0.2 compound under different heat treatment conditions is also discussed. Thermomagnetic analysis shows that the NdCo 6.8Hf 0.2 compound has a Curie temperature of 1065 K. The saturation magnetization of the NdCo 6.8Hf 0.2 compound is 113 emu/g at 5 K and 111 emu/g at 300 K. The compound exhibits a conical magnetic anisotropy at room temperature with a magnetic anisotropy field about 30 kOe. In the NdCo 6.8Hf 0.2 compound, two spin reorientation transitions have been observed at 275 and 400 K, respectively.