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.

Magnetic Characteristics for the Mould-Cast Hard Magnetic Nd70–xFe30Alx ($x=0$ –10) Alloys

“…(7), A and K were also estimated and recorded in Table 2. The results are similar to those obtained by Collocott et al [11,12] .…”

“…The value of r we used here is 40 nm, same to others' work [11] . The criterion for strong pinning in the Gaunt model is…”

“…The ferromagnetic state of the bulk materials results from the freeze of thermal actuation because of magnetic anisotropy when the temperature is below the Tblock. The reason why those clustered materials exhibit hard magnetism has been explained by a lot of models, including a random magnetic anisotropy model [2] , interacting Stoner-Wohlfarth model [10,11] , and a random anisotropy and domain wall pinning process [12] . The domain wall pinning process has been described by the strong pinning model of domain walls of Gaunt [13] .…”