Magnetic and magnetocaloric properties of Mn5Ge3-xSbx

We have studied the magnetic properties of Mn5Ge3-xSbx compounds with x=0, 0.1, 0.2 and 0.3 by means of magnetisation measurements at different temperatures and fields up to 5 T. The compounds crystallize in the hexagonal Mn5Si3-type structure with space group P6(3)/mcm. The compounds show enhanced Curie temperatures but decreasing average magnetic Mn moments with increasing Sb content. The magnetic entropy changes in these compounds are determined from the temperature and field dependence of the magnetisation using the thermodynamic Maxwell relation. Mn5Ge3 exhibits considerably large magnetic entropy changes that are comparable with that of Gd metal. The Sb substitution has two kinds of effects on the magnetocaloric effect (MCE) of Mn5Ge3-xSbx. One is the magnetic entropy change that decreases with increasing Sb content, the other is the MCE peak that becomes broadened. (C) 2002 Elsevier Science B.V. All rights reserved.