Abstract
We have investigated the magnetic properties of epitaxially grown trilayers for different thickness combinations of the NiO spacer and of the Fe overlayer. The magneto optical Kerr effect has been exploited to study the in-plane magnetization reversal processes in the iron layers. Further information has been obtained by means of spin polarized inverse photoemission spectroscopy. We show the existence of a critical value of the NiO thickness for the magnetic coupling between the Fe layers at zero applied field: for the magnetization directions align perpendicularly, while the alignment is collinear for thicker spacers. A phenomenological model has been developed to reproduce the reversal properties of the trilayer and determine the dependence of the coupling energy between the Fe ferromagnetic layers as a function of their relative orientation. We find that the observed behavior cannot be reproduced by a Slonczewski’s coupling term, but rather it is obtained when a biquadratic term is employed.
2 More- Received 5 August 2004
DOI:https://doi.org/10.1103/PhysRevB.72.174402
©2005 American Physical Society