Magnetic transitions in the Gd_5Si_(4-x)P_x (x = 0.5, 0.75,1.25) phases--Magnetocaloric effect of the Gd_5Si_(2.75)P_(1.25) phase

摘要

The Gd_5Si_(2.75)P_(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, DELTA S, reaches the maximum value of -7.8J/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 AS points to the presence of a conventional magnetocaloric effect. Gd_5Si_(3.5)P_(0.5) and Gd_5Si_(3.25)P_(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_(3.25)P_(0.75).