Negative magnetocaloric effect at the antiferromagnetic to ferromagnetic transition of Mn3GaC

The magnetocaloric effect of Mn3GaC, which shows an antiferromagnetic to ferromagnetic transition at 165 K has been investigated. In this compound, magnetocaloric effect obtained at the transition is opposite to that of ordinary ferromagnetic systems, namely, negative magnetocaloric effect. It was found that a large magnetic entropy change, DeltaS(mag), of 15 J/kg K is obtained under an applied field of 2 T. The adiabatic temperature change, DeltaT(ad), reaches 5.4 K in a field change of 2 T. At higher magnetic fields, both DeltaS(mag) and DeltaT(ad) retain a large value over wide temperature range, exhibiting characteristic temperature dependence of a trapezoidal shape. These features are attributed to a sharp first-order transition retained in high magnetic fields as well as small magnetocrystalline anisotropy. (C) 2003 American Institute of Physics.