Regensburg 2019 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Magnetism Poster A

MA 15.77: Poster

Dienstag, 2. April 2019, 10:00–13:00, Poster E

Investigation of Granular Magnetic Exchange Coupled Nano-Composites — •Runbang Shao, Siming Zou, Balati Kuerbanjiang, and Ulrich Herr — Institut für Mikro- und Nanomaterialien, Universität Ulm, Ulm, Deutschland

Exchange coupling of ferromagnetic (FM) nanoparticles to antiferromagnets (AF) can increase the coercivity and the stability against superparamagnetic fluctuations. It has potential applications in further increasing the storage density of hard disk drive and manufacturing permanent magnets with high energy products. We have studied nano-composites with FM Co or Ni nanoparticles embedded in AF FeMn or IrMn thin films. To determine the average size of nanoparticles, the superparamagnetic room-temperature m-H curves of reference samples with FM nanoparticles embedded in non-magnetic Cu films are fitted using a superposition of Langevin functions calculated for varying particle size. The fitted size distribution agrees well with the result obtained by T-SEM analysis of free standing nanoparticles. After application of a field cooling procedure, exchange bias is observed for both Ni/IrMn and Co/FeMn samples at 10K. We observe a pronounced dependence of the exchange bias on FM volume filling factor. Blocking temperatures are determined via zero field cooled (ZFC) and field cooled (FC) measurements. Comparison of the blocking temperatures of nanoparticles embedded in AF films and nanoparticles embedded in non-magnetic films reveals the influence of the exchange coupling on the magnetic energy landscape.