PRESSURE-DEPENDENCE OF THE CURIE-TEMPERATURE OF CO2TIAL

Electrical-resistivity measurements at temperatures between 1.2 and 30 0 K and pressures up to 12 kbar have been used to determine that the p ressure dependence of the Curie temperature T(C) of the ferromagnetic Heusler alloy Co2TiAl is -0.7 K/kbar. Analysis of the pressure depende nce of T(c) in the Stoner-Wohlfarth theory of weak itinerant ferromagn etism reveals the important role of spin fluctuations in this material . Strong ferromagnetic ordering exists only in a limited range of near est-neighbor cobalt-cobalt spacing in itinerant ferromagnets whose onl y potentially magnetic species is Co. Observation of the lack of corre lation between Curie temperature and intermoment cobalt spacing is com bined with the results of high-pressure measurements to identify cobal t Heusler alloys as examples of weak itinerant ferromagnets in which s pin fluctuations are generically expected to make a significant contri bution.