Gas-solid reaction of Nd(Fe, M)_12 (M = Ti, V, Mo) with H, C and N and intrinsic magnetic properties of the interstitially modified compounds

摘要

The influence of interstitial H, C and N atoms on structure and intrinsic magnetic properties of Nd(Fe, M)_12Z_y (M = Ti, V, Mo; Z = H, C, N) was studied. Interstitial hydrogen uptake is reversible, expands the lattice and has a small, but positive effect on the intrinsic magnetic properties. Upon C and N absorption, the ThMn12-type crystal structure is preserved in the case of M = Mo, but a decomposition process and strong growth of the content of α-Fe is observed at temperatures above 450°C for M = Ti or V. Along with this decomposition process, a deterioration of the magnetic properties (measured at room temperature) occurs. For M = Ti or V, the highest values of the Curie temperature, saturation polarization and anisotropy field were found just before the decomposition process starts. For M = Mo, the Curie temperature and anisotropy field have the highest values for Z = N, with maxima for a nitrogen concentration of 1 per formula unit. At low temperatures, the high field magnetization curves of all carburized compounds investigated show a metamagnetic transition when the field is applied perpendicularly to the aligned c-axes of the epoxy bonded powders.