High magnetic field investigation of the field-induced transition in the Nd2Fe17Hx compounds

Abstract

Nd 2 Fe 17 H x compounds are investigated by high-field magnetization measurements performed up to 230 kOe in the 4.2–300-K temperature range. It is shown that the magnetic properties of the Nd2Fe17Hx (x=1, 1.5, 2, 3, 4.9) compounds are very sensitive to the hydrogen content. Insertion of hydrogen within the crystal structure induces a large increase in the Curie temperature. The saturation magnetization is also very sensitive to the hydrogen content, but exhibits a peculiar behavior depending on the hydrogen content. The first-order anisotropy parameter decreases continuously when the hydrogen content increases. A metamagnetic field-induced transition is observed for four Nd2Fe17Hx hydrides corresponding to x=1, 1.5, 2, 3. This metamagnetic transition manifests itself by a step in the magnetization curves recorded when the field is perpendicular to the alignment direction. The temperature dependence of the field at which the transition occurs is determined for all the studied compounds. The thermal evolution of this metamagnetic transition as well as its evolution versus the hydrogen content has been determined. The field-induced transition remains present up to temperatures close to 250–300 K.