Temperature dependence of the spontaneous remagnetization in Nd60Fe30Al10 and Nd60Fe20Co10Al10 bulk amorphous ferromagnets

Abstract

Time dependent behavior of the magnetization, i.e., magnetic viscosity, in ferromagnetic materials is well known. Less well known is the phenomenon of spontaneous remagnetization, where following a magnetic history that results in the dc demagnetized state, a ferromagnetic material spontaneously develops a magnetic moment as a function of time. Spontaneous remagnetization behavior of the bulk amorphous ferromagnets Nd60Fe30Al10 and Nd60Fe20Co10Al10 is investigated as a function of temperature from 50 to 400 K. At all temperatures the spontaneous remagnetization, Mspon, follows the relationship Mspon=Sspon ln(t+t0), where Sspon is a measure of the spontaneous remagnetization processes, t is the time, and t0 is a reference time. Sspon is strongly temperature dependent, increasing approximately linearly with temperature from 50 to ≈300 K, where it reaches a peak, before decreasing rapidly. This behavior is similar to that observed for the magnetic viscosity coefficient, S, in ferromagnetic materials.