Magnetic properties of thulium-hydrogen solid solutions

Low-temperature magnetisation measurements for various fields (10-50 kOe) on solid solutions of alpha TmH x (x taking values from 0 to 0.1) have revealed a decrease of T N and T C with increasing x; the deduced values of the paramagnetic Curie temperature, theta p , and of the effective paramagnetic moment, mu eff p , also decrease with increasing x. The saturation magnetic moment, mu sat (0), increases with increasing field, the addition of hydrogen accelerating this increase. The results are explained in the framework of the RKKY model, assuming an H-H pair structure for the hydrogen configuration, which favours the magnetisation due to the c axis alignment of both pair axis and spins.