The influence of gallium on the magnetocaloric properties of Gd5Si2Ge2

Abstract

Gd5Si2Ge2 was alloyed with varying amounts of Ga to study its influence on the giant magnetocaloric effect. Investigations on Gd-5(Si2-xGe2-x)Ga-2x with 2x = 0.03, 0.05 and 0.13 were carried out using X-ray powder diffraction, temperature and magnetic field dependent magnetization measurements, and differential scanning calorimetry. We observe that as the Ga content increases, the temperature stability range of the monoclinic phase narrows, and the orthorhombic structure gains stability. This is expected to be related to the decrease in the (Si/Ge)-(Si/Ge) bond distance in the monoclinic phase. The maximum entropy change for the parent compound at 270 K was found to be 9.8 J kg(-1) K-1 in an applied field of 5 T. For 2x = 0.03, this value reduces to 8.5 J kg(-1) K-1, and the temperature corresponding to the maximum entropy change shifts marginally to 278 K. For other 2x values, the maximum entropy change further decreases. (C) 2007 Published by Elsevier B.V.