Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 17: Poster Session I

MA 17.9: Poster

Dienstag, 8. März 2016, 09:30–12:30, Poster B1

Exchange Bias in Granular Ferromagnet/Antiferromagnet Nanostructures — •Runbang Shao, Benjamin Riedmüller, Balati Kuerbanjiang, and Ulrich Herr — Institut für Mikro- und Nanomaterialien, Universität Ulm, Ulm, Deutschland

Exchange bias of ferromagnetic (FM) nanoparticles could be used to beat superparamagnetic limit, and the storage density of hard disk drive can be increased subsequently. For such application, a nanostructure with Ni nanoparticles embedded in an antiferromagnetic (AF) IrMn matrix is investigated. To determine the average size of the nanoparticles, the superparamagnetic m-H curve of Ni nanoparticles embedded in a diamagnetic matrix at room temperature is fitted using a superposition of Langevin functions. The fitted log-normal size distribution coincides with the result obtained by T-SEM analysis of unembedded Ni particles. After a field cooling procedure, exchange bias is observed for 10 nm Ni nanoparticles embedded in a IrMn matrix at 10 K. The exchange bias dependence on the Ni volume filling factor is studied. The exchange bias increases with the decreasing Ni volume filling factor up to a maximum of 650 Oe. By modeling the dependence of exchange bias on FM volume filling factor we conclude that a shell of AF material with a minimum thickness of 5.7 nm is needed around one Ni nanoparticle to achieve the largest exchange bias.