Direct Measurements of Magneto-caloric Effect of Gd5Si2Ge2 Alloys in Low Magnetic Field

Direct measurements of the magneto-caloric effect of Gd5Si2Ge2 alloys under heat treatment conditions are investigated by measuring adiabatic temperature change (Delta T (ad)) in a magnetic field of 1.5 T using a homemade magnetocaloric effect measuring apparatus. The crystal structure, microstructure as well as the chemical composition of the alloys are measured using X-ray diffraction (XRD), scanning electron microscope (SEM) with energy dispersive X-ray Detector (EDX). It is found that the microstructure of the alloys could be fully homogenized and the impurities in the alloys could be remarkably removed via appropriate heat treatment. As a result, the maximum adiabatic temperature change (Delta T (ad)) of the alloy annealed at 1573 K increases by 105% from 1.9 to 3.9 K for a magnetic field change from 0 to 15 kOe when compared to the as arc-melted material, while the magnetic ordering temperature slightly reduced.