Low-temperature magnetization in Ni-rich gamma-Ni100-x-yFexVy alloys

Detailed studies of the temperature dependence of the spontaneous magnetiza tion have been made in eight different compositions of gamma-Ni100-x-yFexVy (4 less than or equal to x less than or equal to 17; 2 less than or equal to y less than or equal to 18) alloys at a magnetic field of 30 kOe between 4.2 and 50 K. The values of the Curie temperature (Tc) and the saturation magnetization (Mo) an found to decrease with the increase of V. This is und erstood since the addition of V (which is antiferromagnetic) suppresses the ferromagnetic order in the NiFe binary alloys. The magnetization of the al loys with low V (y less than or equal to 11 at. %) has shown a good fit to only the spin-wave T-3/2 term whereas the data for the high V (gamma greate r than or equal to 12 at. %) alloys require an additional Stoner T-2 term ( for weak itinerant ferromagnets). This indicates that the addition of more V gives the alloys a weak itinerant electron character. The range of temper ature of the above analysis is much lower than 0.1T(C) for most of the allo ys. Also, the Arrott plots near Te show a set of almost parallel isothermal lines supporting the presence of the Stoner term. Thus the present magneti zation studies show convincingly a transition from the localized to the wea k itinerant electron ferromagnetism in the high V (gamma greater than or eq ual to 12 at. %) alloys.