Magnetic transitions in the Gd 5Si 4− xP x ( x = 0.5, 0.75, 1.25) phases. Magnetocaloric effect of the Gd 5Si 2.75P 1.25 phase

Abstract

The Gd 5Si 2.75P 1.25 phase with all interslab Si/P–Si/P dimers broken (Sm 5Ge 4-type structure) undergoes a ferromagnetic transition at 184 K. For this phase, the magnetocaloric effect in terms of the magnetic entropy change, Δ S, reaches the maximum value of −7.8 J/kg K at 177 K. Absence of a temperature-dependant structural transition, as confirmed by the low-temperature single crystal diffraction studies, together with the moderate value of Δ S points to the presence of a conventional magnetocaloric effect. Gd 5Si 3.5P 0.5 and Gd 5Si 3.25P 0.75, which are composites of the Gd 5Si 4- (all Si/P–Si/P dimers intact) and Sm 5Ge 4-type phases, possess two magnetic transitions associated with the two-phases. Introduction of P into Gd 5Si 4 lowers the Curie temperature from 336 K to 332 K in Gd 5Si 3.25P 0.75.