Microscopic origin of exchange bias in core/shell nanoparticles

Abstract

We report the results of Monte Carlo simulations with the aim to clarify the\nmicroscopic origin of exchange bias in the magnetization hysteresis loops of a\nmodel of individual core/shell nanoparticles. Increase of the exchange coupling\nacross the core/shell interface leads to an enhancement of exchange bias and to\nan increasing asymmetry between the two branches of the loops which is due to\ndifferent reversal mechanisms. A detailed study of the magnetic order of the\ninterfacial spins shows compelling evidence that the existence of a net\nmagnetization due to uncompensated spins at the shell interface is responsible\nfor both phenomena and allows to quantify the loop shifts directly in terms of\nmicroscopic parameters with striking agreement with the macroscopic observed\nvalues.\n