LAUSR

Abstract We investigate the effect of hydrogen insertion on the microstructure and magnetic properties of nanocrystalline Pr 2 Co 7 H x (0 ≤ x ≤ 3.75) hydrides. The Pr 2 Co 7 H x hydrides were characterized by X-ray diffraction (XRD) and physical properties measurement system (PPMS9) Quantum Design. Mean field theory was used to describe the temperature dependence of magnetization and deduce the exchange interactions and Curie temperature. We also apply the approach to saturation magnetization to our system. The results were interpreted in the framework of random magnetic anisotropy model. From such analysis, some fundamental parameters were extracted. We have determined the local magnetic anisotropy constant K 1 which is found to increase from 5.2 × 10 7  erg/cm 3 to a maximum of 5.7 × 10 7  erg/cm 3 with increasing x from 0 to 2.5, respectively. This confirms the hypothesis of the electronic and magnetovolume effect of hydrogen insertion. In addition, it is shown that Herzer theory describes satisfactory the experimental data of change of coercive field as a function of grain size.