Magnetic relaxation in Fe-(SiO₂) granular films

Authors

Gang Xiao, Johns Hopkins UniversityFollow
Sy_Hwang Liou, University of Nebraska-LincolnFollow
A. Levy, Johns Hopkins University
J.N. Taylor, Johns Hopkins University
C. L. Chien, Johns Hopkins University

Date of this Version

12-1-1986

Comments

Published by American Physical Society. Phys. Rev. B34, 7573 (1986). http://prb.aps.org. Copyright © 1986 American Physical Society. Permission to use.

Abstract

Magnetic relaxation of granular Fe-(SiO₂) solids with low metal-volume fraction has been studied by employing dc SQUID (superconducting quantum interference device) magnetometry and Mössbauer spectroscopy with the characteristic measuring time differing by nine orders of magnitude. The blocking temperatures (T_B), extrapolated to zero external field as measured by the two techniques maintain a constant ratio of 0.35 independent of samples. Arrhenius law was found adequate in describing the relaxation process, with a well-defined relaxation-time constant of τ₀≃10^-13 sec. A cusp in the susceptibility is observed at T_B, below which irreversible difference between the field-cooled and zero-field-cooled magnetizations occurs. Despite this spin-glass-like behavior, granular magnetic systems are found to be fundamentally different from spin glasses.