Exchange bias and asymmetric hysteresis loops from a microscopic model of core/shell nanoparticles

Abstract

We present Monte Carlo simulations of hysteresis loops of a model of a magnetic nanoparticle with a ferromagnetic core and an antiferromegnetic shell with varying values of the core/shell interface exchange coupling which aim to clarify the microscopic origin of exchange bias observed experimentally. We have found loops shifts in the field direction as well as displacements along the magnetization axis that increase in magnitude when increasing the interfacial exchange coupling. Ovelap functions computed from the spin configurations along the loops have been computed to explain the origin and magnitude of these features microscopically.Comment: 3 pages, 3 figures. To be presented at the 3rd JEMS 2006, San Sebastian (Spain), June 26-30th 2006; Exchange Bias Symposium. More information at this web page: http://hermes.ffn.ub.es/oscar/Articles.htm