Neutron diffraction study of LaFe11.31Si1.69 and LaFe11.31Si1.69H1.45 compounds

The structural and magnetic properties of LaFe11.31Si1.69 and LaFe11.31Si1.69H1.45 compounds have been studied by neutron diffraction. Besides, characterization and optimization of their magnetocaloric properties, we have investigated more fundamental aspects of their crystal and magnetic structures. From high statistics neutron powder diffraction experiments, we have determined the cell parameters, the atomic positions, the atom occupancies, the interatomic distances and the magnetic moments versus temperature. An increase of specific Fe-Fe distances upon hydrogen absorption was pointed out leading to the net increase of the Curie temperature, well supported by the strong dependence of the Fe-Fe exchange interaction with metal-metal distances.