Dilution-induced enhancement of the blocking temperature in exchange-bias heterosystems

Authors

Xi Chen, Laboratorium fu¨r Angewandte Physik, Gerhard-Mercator-Universita¨t Duisburg, 47048 Duisburg, Germany
Christian Binek, University of Nebraska-LincolnFollow
A. Hochstrat, Laboratorium fu¨r Angewandte Physik, Gerhard-Mercator-Universita¨t Duisburg, 47048 Duisburg, Germany
Wolfgang Kleemann, Laboratorium fu¨r Angewandte Physik, Gerhard-Mercator-Universita¨t Duisburg, 47048 Duisburg, GermanyFollow

Date of this Version

December 2001

Comments

Published by American Physical Society. ©2002. Permission to use. Phys. Rev. B 65, 012415 (2002).

Abstract

The temperature dependence of the exchange bias field is investigated by superconducting quantum interference device magnetometry in Fe_1-xZn_xF2(110)/Fe14 nm/Ag35 nm, x=0.4. Its blocking temperature exhibits a significant enhancement with respect to the global ordering temperature T_N=46.9 K, of the bulk antiferromagnet Fe_0.6Zn_0.4F₂. The enhancement is attributed to fluctuations of the diamagnetic dilution which creates clusters on all length scales having a Zn dilution of 0<~x<~1. While the infinite clusters give rise to the well-known Griffiths phase, finite clusters also provoke a local enhancement of the exchange bias. The temperature dependence of the integral exchange bias effect is modeled by averaging all local contributions of the antiferromagnetic surface magnetization which exhibit a surface critical behavior.