Berlin 2005 – scientific programme

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MA: Magnetismus

MA 31: Magnetische Partikel/Cluster II

MA 31.5: Talk

Wednesday, March 9, 2005, 12:00–12:15, TU H1012

Classifying magnetic interactions in nanoparticle assemblies using Cole-Cole plots — •Oleg Petracic¹, Andreas Glatz², Subhankar Bedanta¹, Xi Chen¹, and Wolfgang Kleemann¹ — ¹Angewandte Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany — ²Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany

Studying the magnetic ac susceptibility, χ = χ′ − i χ″, of nanoparticle assemblies leads to important conclusions about the role of inter-particle interactions. We demonstrate that the Cole-Cole plot, χ″ vs. χ′, can be used as a tool for classifying the magnetic behavior of interacting or non-interacting nanoparticles. Distinguishing non-interacting superparamagnetic from collective behavior like in the superspin glass or superferromagnetic state is easily possible. We performed measurements of the magnetization hysteresis and ac susceptibility on the granular multilayer [Co₈₀Fe₂₀/Al₂O₃]_n. The results are successfully compared to simulations within two approaches for a driven domain wall in random media.