Origin of the anomalous temperature dependence of the Nd sublattice magnetization in Nd 2Fe 14B

Abstract

The anomalous temperature dependence (kink) of the Nd magnetic moments in Nd 2Fe 14B, observed in the temperature dependence of (i) the spontaneous magnetization and (ii) the 145Nd hyperfine fields, has been explained in terms of the NdFe exchange and the crystal field interactions, neglecting the NdNd exchange interaction. The set of crystal field parameters employed in this analysis also describes other experimental data such as (i) the first order magnetization processes occuring along the [1 0 0] direction at low temperatures, (ii) the tilted spin structure and (iii) the spin reorientation at 135 K. It has been shown that the kink mainly comes from the crystal field induced canted spin structure and is directly related to the macroscopic anisotropy energy. The corresponding anomalous temperature dependence in the Nd ions' energy levels predicted by our model agrees well with the results of inelastic scattering measurements.