Neutron-diffraction study of the insertion scheme of hydrogen in Nd2Fe14B

Abstract

Results are presented of a neutron powder diffraction experiment performed at room temperature on the Nd2Fe14BHx series. The location of the hydrogen (or deuterium) atoms within the crystal lattice is described. After an analysis of the crystal structure of Nd2Fe14B, Nd2Fe14BH, Nd2Fe14BH2, Nd2Fe14BH3, and Nd2Fe14BH4, a filling scheme of the interstitial sites by hydrogen atoms is proposed. This filling scheme is compared and discussed with that previously obtained on other R2Fe14B alloys in particular with R=Ce, Y, Ho, Er. The use of all these compositions provides a better understanding of the way the Nd2Fe14B structure is modified by insertion of hydrogen. The evolution of the shortest iron-iron interatomic distances is also analyzed and related to the change in magnetism.