Investigation of the metamagnetic transition in Y2Co7H6.

Olivier Isnard (1) , Claudia Lotea (1) , François Baudelet (2, 3)

1 Laboratoire de Cristallographie
2 LURE - Laboratoire pour l'utilisation du rayonnement électromagnétique
3 IMPMC - Institut de minéralogie et de physique des milieux condensés

The effects of hydrogen absorption on the crystalline and magnetic properties of the γ-phase Y2Co7H6 were examined by bulk magnetic measurements, neutron diffraction and X-ray absorption spectroscopy. An orthorhombic distortion of the unit cell occurs upon hydrogen insertion, accompanied by a reduction of the magnetic moment on Co and a decrease of the ordering temperature. Magnetic measurements indicate a metamagnetic transition occurring in the γ-phase hydride. The transition shows a broad hysteresis and the magnitude of the critical field is found to decrease with increasing temperature. The electronic structure of Co in Y2Co7 and Y2Co7H6 has been investigated by X-ray absorption spectroscopy. The observed decrease of the pre-peak intensities in the Co-K edge XANES spectra are related to the changes of the 4p–3d density of states upon hydrogen insertion. A comparative X-ray magnetic circular dichroism investigation at the Co-K edge has been carried out for Y2Co7 and Y2Co7H6. The observed XMCD signal enables us to propose that ferromagnetic ordering occurs in the γ-hydride.

Mots clés: Cobalt compound; Hydride; X-ray absorption spectroscopy; Magnetic circular X-ray dichroism

Domaines: Physique [physics]

Olivier Isnard, Claudia Lotea, François Baudelet. Investigation of the metamagnetic transition in Y2Co7H6.. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005, 238, pp.229-232. ⟨10.1016/j.nimb.2005.06.052⟩. ⟨hal-00020248⟩