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He-ion bombardment induced exchange bias modifications : Fundamentals and applications

Details zur Publikation
Ehresmann, A.
Recent research developments in applied physics

Zusammenfassung, Abstract
The exchange bias effect (EB) in antiferromagnet/ ferromagnet (AF/F) systems characterized by a shift of the hysteresis loop of the ferromagnet with respect to the zero magnetic field results from the exchange interaction between AF and F, i.e. to magnetically saturate the F antiparallel to the direction of its unidirectional anisotropy an additional magnetic field must be applied, the so called exchange bias field Heb. The EB is usually initiated by annealing the sample in the presence of a magnetic field and, therefore, uniform within the complete sample. Recently a method was developed to increase and decrease Heb by bombardment with light ions in a magnetic field. With the same technique it is also possible to change the direction of the unidirectional anisotropy. Even an initialization of the exchange bias is possible. In combining the ion bombardment with lithographical techniques a lateral magnetic patterning becomes feasible. In this review the principle observations of the keV He-ion bombardment induced modifications of Heb and of the accompanying coercive field He will be described. A first model of the physics governing the ion bombardment induced magnetic modifications in the polycrystalline AF/F layers will be presented. Connected with this it will be shown that the grain size distribution of the polycrystalline layers, particularly in the AF, is of essential importance. The applications of the ion bombardment induced Heb modifications for the use in gaint magnetoresistance (GMR) and tunnel magnetoresistance (TMR) layer stacks and in sensors will be presented. The technique of ion bombardment induced lateral magnetic patterning (IBMP) will then be described. Finally investigations of the lateral magnetic patterns by, e.g., magnetic force microscopy (MFM) will be presented.

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Zuletzt aktualisiert 2019-25-07 um 14:25