[Zurück]

H. Forster, N. Bertram, X. Wang, R. Dittrich, T. Schrefl:
"Energy barrier and effective thermal reversal volume in columnar grains";
Journal of Magnetism and Magnetic Materials, 267 (2003), S. 69 - 79.

Energy barrier and effective thermal reversal volume in columnar grains

Hermann ForsterCorresponding Author Contact Information, E-mail The Corresponding Author, a, Neal Bertramb, Xiaobin Wangb, Rok Dittricha and Thomas Schrefla

a Vienna University of Technology, Wiedner Hauptstr. 8-10, Vienna A-1040, Austria
b UCSD, San Diego, USA

Received 19 December 2002; revised 20 March 2003. Available online 1 May 2003.


Abstract

A method to determine the minimum energy path between two stable states in a magnetic system is used to investigate magnetic reversal of an irregularly shaped columnar grain. The method describes the magnetization reversal process initiated by thermal excitations in zero applied field or fields below the intrinsic switching field. In addition to the energy barrier, an effective volume Veff is calculated as a function of material exchange interaction, uniaxial crystalline anisotropy, and particle length. The minimum energy barrier paths follow that of intrinsic switching where with decreasing exchange the reversal modes go from uniform rotation to end nucleation and subsequent expansion to reversal by vortex excitation. The effective reversal volume decreases with decreasing exchange and increasing crystalline anisotropy. Decreasing the particle length also decreases the effective volume once the length becomes less than the excitation length. A very simple analytic wall model nicely indicates these trends. Analysis of measured thermal reversal fields for CrO2 and Fe explain the inferred effective volumes in these particles.

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC04970157

http://dx.doi.org/10.1016/S0304-8853(03)00306-8