Deuteride absorption and desorption effects on magnetic properties of YFe2D<i>x</i>

Abstract

Magnetic properties of YFe2 and its deuterides YFe2Dx have been investigated in the temperature range 300&amp;lt;T&amp;lt;800 K. Both the lattice structure and the Curie temperature Tc show strong dependence on the deuterium composition x. The deuterides have a C15 cubic structure up to x=2.7 and Tc rises from 560 K for x=0, up to 715 K for x=2.2 and 2.7. Amorphous YFe2D2.3 was also synthetized and surprisingly displays a lower Tc=330 K. For larger deuterium concentrations, the deuterides show a rhombohedral distortion and the Curie temperature is reduced. Rhombohedral deuteride YFe2D3.6 has Tc=345 K. Heating this deuteride above 410 K leads to partial desorption of the deuterium and transformation of the material into a cubic phase. This is evidenced by the fact that a spontaneous magnetization at these high temperatures is restored, characteristic of cubic deuterides with x≤2.7. On the other hand, additional desorption upon heating above 700 K induces a transition to the amorphous state, as a result of the weakening of the Y—Fe bond. The time dependence of the magnetization at a given temperature shows that the desorption at high temperature is due to the diffusion of deuterium through the surface.