Magnetic moment of iron–nickel invar alloys from 4 to 80 K

Abstract

The magnetic moment of several ferromagnetic face-centered-cubic iron–nickel alloys in the invar region have been investigated at low temperatures, as a function of both the magnetic field and the temperature. A vibrating-sample magnetometer was used, for which relative changes in the moment of 3 parts in 10 5 could be resolved. Such resolution has permitted a detailed analysis of the temperature dependence of ΔM/M, the relative deviation of the magnetic moment from its value at 0 K, in terms of a contribution arising from spin-wave excitations, varying as T 3/2 , and one from single-particle excitations, varying as T 2 , both of these at constant volume, together with a term describing the effect of volume dilation on the moment. The fits to the data for H = 10 kOe yield, for 34 at. % Ni:[Formula: see text]and for 40 at. %Ni:[Formula: see text]