Journal article
On the origin of ion bombardment induced Exchange Bias modifications in polycrystalline layers



Publication Details
Authors:
Ehresmann, A.; Junk, D.; Engel, D.; Paetzold, A.; Röll, K.
Publication year:
2005
Journal:
Journal of Physics D: Applied Physics
Pages range:
801-806
Volume number:
38
ISSN:
0022-3727

Abstract
A model for the modifications of the exchange bias (EB) field Heb of antiferromagnet (AF)/ferromagnet (F) bilayers with a polycrystalline or multidomain AF layer induced by ion bombardment (IB) in an external magnetic field is proposed. The model is based on a known two-energy level model for an antiferromagnetic grain or domain in contact with a ferromagnet where two free energy minima are separated by an energy barrier. The model explains the as yet unexplained increase of Heb upon IB on the basis of the grain/domain size and magnetic anisotropy constants distributions in the antiferromagnetic layer after its deposition and on the basis of a twofold effect of the IB on the antiferromagnetic grains/domains: (1) IB acts like local hyperthermal heating leading to an almost immediate increase of the sample's EB. (2) Defects induced by IB in the antiferromagnetic grains/domains lead to a decrease of the energy barrier between the two minima, resulting in a slow additional increase of Heb with time (with temperature T as a parameter) after the bombardment. The model is tested by experiments on the time dependence of the EB and coercive fields after the IB of NiO/NiFe bilayers.


Research Areas


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