Eur. Phys. J. B 35, 3-12 (2003)
https://doi.org/10.1140/epjb/e2003-00250-0

Dynamic susceptibility of reentrant Fe-rich inhomogeneous amorphous alloys

¹ Departamento CITIMAC, F. Ciencias, Universidad de Cantabria, Santander 39005, Spain
² Departamento de Física, Universidad de Oviedo, Oviedo 33007, Spain
³ Dept. Elec. y Electrónica, F. Ciencias, Universidad del País Vasco, Bilbao 48080, Spain

Corresponding author: ^a barquinl@unican.es

Received: 11 March 2003
Revised: 13 May 2003
Published online: 22 September 2003

Abstract

Melt-spun amorphous alloys of Fe₉₁Zr₉, Fe₉₁Zr₇B₂, Fe₉₀Zr₇B₃ and Fe₈₈Zr₈B₄ have been characterized by AC susceptibility at frequencies between 30 Hz and 10 KHz. The measurements reflect the existence of reentrant spin glass transitions below 40 K for all cases. The transition shift per frequency decade is large compared to the observed in conventional spin-glass alloys. The shift value increases with the boron content and becomes closer to values in fine-particle systems. We find that the relaxation in Fe₉₁Zr₉ follows a critical slowing down at the reentrant transition, with exponents and . The non-linear susceptibility displays a peak at the transition in this alloy, but wider than in canonical spin glasses. A Vogel-Fulcher (VF) activation process can explain the frequency variation in all the Fe-Zr-B alloys. The reduction of the ideal glass temperature in the VF approach, found in the higher Boron content alloys, is an indication of a superparamagnetic-like behavior. The behavior shown by these alloys is intermediate between a collective freezing and superparamagnetic-like relaxation. We propose that this is arising due to a heterogeneous spin structure. The inclusion of a reduced amount of B, affects the magnetic spin structure.