Enhanced Magnetic Entropy in Gd Ni2

Abstract

Measurements of the specific heat have been performed on Gd1-x Yx Ni2 (x=0,0.2) compounds and their nonmagnetic analogs Lu1-y Yy Ni2, which have similar molar masses. It is found that the difference between the entropies of magnetic and nonmagnetic compounds with identical molar masses surpasses substantially (by 14-19%) the theoretical limit for the magnetic contribution Sm = (1-x) R ln (8) calculated assuming that only Gd ions possess a magnetic moment. This observed enhancement of the magnetic entropy in Gd1-x Yx Ni2 is believed to result from spin fluctuations induced by f-d exchange in the 3d electron subsystem of Ni. © 2007 The American Physical Society.