THE DISCOVERY OF WEAK METALLIC FERROMAGNETISM WITH A HIGH CURIE-TEMPERATURE

A ternary intermetallic compound containing elements which themselves do not order magnetically has been found to have a spontaneous magneti sation. The compound, Pd2TiSn, is crystallographically ordered in the L2(1) structure with a lattice parameter of 6.38 Angstrom. Magnetisati on measurements indicate a ferromagnetically ordered moment per formul a unit of sigma = 0.005 mu(B) which essentially does not change with t emperature over the range of 2 to 300 K. Over this temperature range, magnetic hysteresis was observed, confirming the existence of a ferrom agnetic state. Arrott plots reveal that the isotherms in the high fiel d region are characterised by straight lines which, over the temperatu re range investigated, converge approximately to a single point on the sigma(2) axis. Such behaviour can be accounted for if the coefficient s in the free energy expansion giving rise to Arrott plots have a simi lar temperature dependence. A description of these observations is giv en in terms of a band model.