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

Abstract

Detailed studies of the temperature dependence of the spontaneous magnetization 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 understood since the addition of V (which is antiferromagnetic) suppresses the ferromagnetic order in the NiFe binary alloys. The magnetization of the alloys 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 greater 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 temperature of the above analysis is much lower than 0.1T(C) for most of the alloys. Also, the Arrott plots near Te show a set of almost parallel isothermal lines supporting the presence of the Stoner term. Thus the present magnetization studies show convincingly a transition from the localized to the weak itinerant electron ferromagnetism in the high V (gamma greater than or equal to 12 at. %) alloys.