ΔB mechanism for fringe-field organic magnetoresistance

M. Cox, S. P. Kersten, J. M. Veerhoek, P. Bobbert, and B. Koopmans
Phys. Rev. B 91, 165205 – Published 23 April 2015

Abstract

Fringe fields emanating from magnetic domain structures can give rise to magnetoresistance in organic semiconductors. In this article, we explain these magnetic-field effects in terms of a ΔB mechanism. This mechanism describes how variations in magnetic-field strength between two polaron hopping sites can induce a difference in precessional motion of the polaron spins, leading to mixing of their spin states. In order to experimentally explore the fringe-field effects, polymer thin-film devices on top of a rough in-plane magnetized cobalt layer are investigated. The cobalt layer can be described by a distribution of out-of-plane magnetic anisotropies, most likely induced by thickness variations in the cobalt. With a magnetic field perpendicular to the cobalt layer, fringe fields are created because some domains are magnetized out of plane whereas the magnetization of other domains remains approximately in plane. By varying the distance between the polymer layer and the cobalt layer, we find that the magnetoresistance arising from these fringe fields reduces with the gradient in the fringe fields, in agreement with the ΔB mechanism.

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  • Received 14 November 2014
  • Revised 21 March 2015

DOI:https://doi.org/10.1103/PhysRevB.91.165205

©2015 American Physical Society

Authors & Affiliations

M. Cox, S. P. Kersten, J. M. Veerhoek, P. Bobbert, and B. Koopmans

  • Department of Applied Physics, Center for NanoMaterials, COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

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Issue

Vol. 91, Iss. 16 — 15 April 2015

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