Regensburg 2002 – wissenschaftliches Programm

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MA: Magnetismus

MA 10: Poster : Dünne Schichten(1-21),Spinabh.Transp.(22-39),Exch.Bias(40-51),Spindyn.(52-55),Mikromag.(56-66),Partikel(67-74),Abb.Verf.(75-77),Oberfl.+Spinelektr.+Elektr.Theo+Mikromag(75-87),PÜ+Aniso+Werkst/Leg.(88-103),Mol.Mag.+N-dim+Messm.+Postdead(104-111

MA 10.67: Poster

Dienstag, 12. März 2002, 15:00–19:00, Bereich A

Phase transition and dynamics of interacting magnetic nanoparticles in discontinuous Co₈₀Fe₂₀/Al₂O₃ multilayers — •S. Sahoo¹, O. Petracic¹, Ch. Binek¹, W. Kleemann¹, J. B. Sousa², S. Cardoso³, and P. P. Freitas³ — ¹Laboratorium für Angewandte Physik, Gerhard-Mercator-Universität Duisburg, D-47048 Duisburg — ²IFIMUP, Departamento de Fisica, Universidade de Porto, 4169-007 Porto, Portugal — ³INESC, Rua Alves Redol 9-1, 1000 Lisbon, Portugal

Random dipolar interactions and anisotropies of ferromagnetic nanoparticles in discontinuous magnetic multilayer systems [Co₈₀Fe₂₀(t)/ Al₂O₃(3 nm)]₁₀ with t = 0.9 and 1.0 nm give rise to a low temperature superspin glass (SSG) state. This has been evidenced by the critical slowing down of relaxation and the divergence of the nonlinear susceptibility. Field dependence studies reveal the existence of a de Almeida-Thouless line below 2 mT, while a crossover into a chiral glass like phase seems to occur at higher fields. Non-equilibrium dynamics such as aging and memory effect have been observed in the SSG phase.