MAGNETIC AND TRANSPORT-PROPERTIES OF FE-3(GA1-XALX)(4) COMPOUNDS

The magnetic phase transitions of the itinerant-electron system Fe-3(G a1-xAlx)(4), with x in the range 0.00 less than or equal to x less tha n or equal to 0.10, are studied by means of magnetisation and (magneto )resistivity measurements. At 65.5 K, with increasing temperature a fi rst-order magnetic phase transition from a ferromagnetic to an antifer romagnetic state is observed for Fe3Ga4. Substitution of Al for Ga res ults in an increase of the transition temperature of 4.1(4) K/at% Al; the low-temperature ferromagnetic state is stabilised with respect to the high-temperature antiferromagnetic state. This behaviour is differ ent to the effect of Co substitution on the Fe sites, where the magnet ism is suppressed, eventually leading to paramagnetism. The results ar e discussed in the framework of the theory on magnetic phase transitio ns in itinerant-electron systems of Moriya and Usami. (C) 1998 Elsevie r Science B.V. All rights reserved.