"Novel states and functions of magnetic and polar solids at the nanoscale"

by Prof. Wolfgang Kleemann (University of Duisburg-Essen)

Wednesday, February 13th, 2019 from 10:00 - 11:30 (Europe/Budapest) 

at KFKI campus (Bldg.1. Conference Room)


Magnetic and electric dipolar interactions give rise to novel states in aggregates of nanoparticles (NPs). In this talk I shall first report on Supermagnetism, the occurrence of different states of magnetic single domain NPs in dense systems. At high densities the superferromagnetic state of FeCo NPs reveals domain walls with specific kinetics. The mesoscopic superspinglass state of dilute FeCo NPs embedded in a film of Al2O3 at low density resembles microscopic spin glasses to a large extent. Superspinglasses belong to the family of Ferroic Glasses along with so-called 'Relaxor Ferroelectrics'. These are disordered ionic solid solutions like PbMg1/3Nb2/3O3, where NPs emerge as polar nanoregions pinned by intrinsic alloy quenched random electric fields and condense into a cluster glass ground state. Magnetic NPs have found strong interest in artificial Nanocomposites with specific interface couplings. I report on bilayered films with stress-strain coupling in BaTiO3/CoFe2O4 and with magnetic exchange coupling in Cr2O3/[Pt/Co/Pt], respectively. Both systems appear promising for applications in novel RAM devices.