Study of RFe9.5Mo2.5H (R = Y, Dy, Ho, Er) and RFe9.5Mo2.5N (R = Y, Dy) compounds by Mossbauer spectroscopy, magnetisation and neutron powder diffraction

RFe9.5 Mo-2.5 H-y (R = Y, Dy, Ho, Er) and RFe9.5Mo2.5Ny (R = Y, Dy) prepare d by gas-solid reaction were studied by X-ray and neutron powder diffractio n, magnetisation and Mossbauer spectroscopy. Hydrogen or nitrogen atoms wer e found to be located in the 2b interstitial site of the tetragonal ThMn12- type structure. A strong increase of the magnetic properties after hydrogen ation or nitrogenation is observed. In hydrides the overall magnetic behavi our is mainly due to the increase of the Fe interatomic distances; in nitri des the magnetic behaviour is essentially controlled by the competition bet ween that effect and the 2p-3d hybridisation. The anisotropic charge redist ribution around the R atom caused by N absorption also plays an important r ole. Mossbauer and neutron experiments performed as a function of temperatu re show that the magnetic characteristics can be interpreted as the result of local magnetic behaviour differentiated for each of the three Fe-sublatt ices, (C) 2000 Elsevier Science B.V. All rights reserved.