Magnetic properties of R-T hydrides (Ho, Y)6Fe23H15

Magnetization measurements M(T,H,x) were performed on ferrimagnetic Ho6-xYxFe23H15 (x=0.47 and 0.92) compounds in the 4.2-700 K temperature range (Curie temperature TC∼600 K) in a magnetic field up to 55 kOe. In comparison to parent alloys, absorption of hydrogen leads to a decreasing compensation temperature, a strong increase of the magnetic moments of the compounds in the 200-400 K temperature range, and a higher Curie temperature. These results are analyzed within the frame of Herbst and Croat refined-Neel molecular field theory model, taking into account the increase of the iron magnetic moment and the weakening of the magnetic exchange coupling NHo-Fe as compared to their alloys values. The mean canting angle between rare earth and iron sublattices θ (θ≤10 deg. ) is important for the yttrium-substituted compounds, particularly in the vicinity of compositions for which Tcomp∼0 K