Magnetic properties of crystalline and amorphous GdCo2Hx hydrides

High-field magnetization curves and temperature dependences of the magnetization have been studied for crystalline and amorphous GdCo2Hx hydrides. Crystalline hydrides with different x≤3.76 isostructural to the parent Laves phase GdCo2 were prepared by hydrogenation in the temperature range 20-160 C at hydrogen pressures 105-103 Pa. The magnetic ordering temperature gradually decreases with increasing x. The magnetic moment of Co decreases from 1.02 μB for x=0 down to nearly zero for x=3.76. Hydrogenation in the temperature range 200-320 C at a hydrogen pressure of 106 Pa leads to the formation of amorphous hydrides. They are ferrimagnets with the compensation point that ranges from 117 to 170 K depending on the amorphization temperature. The high-field magnetization curves indicate a distribution of Gd-Co exchange parameters in the amorphized samples. The average Gd-Co molecular field coefficient nGdCo decreases with increasing the amorphization temperature. The obtained results were interpreted with the assumption of heterogeneous structural state of the amorphous hydrides. (orig.)