Hyperfine field and isomer shift evolution in hydrogenated Nd-Fe-B alloy

F. D. SACCONE, C. E. RODRÍGUEZ TORRES, F. H. SÁNCHEZ AND M. B. FERNÁNDEZ VAN RAAP

HYPERFINE INTERACTIONS

Springer

Año: 2001 vol. 134 p. 123 - 129

0304-3843

RE2Fe14B (RE=rare earth) materials are capable of absorbing hydrogen to form a stable solid solution at room temperature. Hydrogenation produces a number of significant changes in the hyperfine interactions. In this work 57Fe Mössbauer effect spectroscopy and X-Ray diffraction measurements were performed on Nd14.01Hf0.08Fe78.91B7.00 alloys submitted to thermal treatment in hydrogen atmosphere. A non-linear increase of the hyperfine fields and isomer shifts with hydrogen concentration was observed. The hyperfine parameters of the 8j1 site exhibit a rather different evolution than those experienced by the other major sites (8j2, 16k1, 16k2). THe origin of the hyperfine field enhancement is analysed in terms of volume expansionand H nearest neighbors to the iron sites. A linear expression on these two effects to give account of isomer shift evolution for 8j1 site is given.