The substitution effect of boron on reentrant behavior of rapidly solidified Fe–Mn–Zr alloys

We have studied the magnetic properties of boron-substituted amorphous reentrant Fe–Mn–Zr alloys. The magnetic characterization of a-Fe82Mn8−xBxZr10 (numbers indicate at.%) alloys has been done through the studies of thermal variation of magnetization, ac susceptibility and ferromagnetic resonance. Low-temperature spin freezing was observed at 54 K with large coercivity and low magnetic moment for a-Fe82Mn8Zr10. The large coercivity at low temperatures and high freezing temperature for this sample is attributed to magnetic hardening. With an increase of the concentration of B, it is observed that the Curie temperature increases and the spin-glass-like transition observed at low temperature moves to lower temperatures and finally vanishes at x = 8 at.%. A single resonance peak in FMR spectrum was observed below TC and at least two distinct line shapes were observed well beyond the TC for two of the compositions, namely, x = 4 and 6. These observations could be qualitatively understood in terms of a finite spin clusters plus an infinite ferromagnetic matrix model. It can also be concluded that the magnetic disorder is reduced as boron concentration is increased.