The absorption of hydrogen in ternary RFe12-xMx (R=Y or rare earth, M=
Ti, Mo) alloys has been investigated by neutron diffraction. These com
pounds crystallise in the tetragonal (I4/mmm) structure of ThMn12 type
. In this work we report structural and magnetic investigations undert
aken by neutron diffraction for some hydrides with high hydrogen conte
nts and we focus on the location of hydrogen in Ti and Mo containing m
aterials. The effects of hydrogenation on the intrinsic properties suc
h as enhancement of Curie temperature, lattice parameters, Fe moment a
s determined by neutron diffraction, magnetic and Mossbauer measuremen
ts, are discussed.