Magnetocaloric effect in Gd-Sc solid solutions

Abstract

Development of magnetic cooling technology needs effective and suitable solid state refrigerants whose properties meet rigorous functional and market requirements. One of the important issues hindering progress in this field is the lack of a clear understanding of the mechanisms underlying the giant magnetocaloric effect that some materials demonstrate. Considering systems based on one magnetic component seems to be a promising and effective way to unraveling this puzzle. This study is aimed at partially filling this gap by inspecting the magnetic and magnetocaloric properties of a series of GdSc alloys containing up to 25 at.% Sc. It has been established that all obtained alloys form single-phase disordered solid solutions with an hexagonal closed-packed crystal lattice. We found that doping with scandium induces strong distortion effects in the crystal structure due to huge atomic size mismatch. The studied GdSc alloys are ultra-soft ferromagnets with high Curie points. The magnetocaloric response in the alloys is not large in magnitude compared to Gd but the magnetocaloric effect (MCE) extends over a wide temperature interval exceeding 135 K, resulting in the relative cooling power of 930 – 986 J/kg in a magnetic field of 5 T. Such behavior in the MCE is associated with the strongly distorted crystalline structure which provokes complicated magnetic exchange correlations. High density of structural defects in GdSc alloys, induced by large atomic size mismatch, is probably the determining factor in improving the refrigerant capacity.