We report local probe investigations of the magnetic interaction between BiFeO3 films and a ferromagnetic Co0.9Fe0.1 layer. Within the constraints of intralayer exchange coupling in the Co0.9Fe0.1, the multiferroic imprint in the ferromagnet results in a collinear arrangement of the local magnetization and the in-plane BiFeO3 ferroelectric polarization. The magnetic anisotropy is uniaxial, and an in-plane effective coupling field of order 10 mT is derived. Measurements as a function of multiferroic layer thickness show that the influence of the multiferroic layer on the magnetic layer becomes negligible for 3 nm thick BiFeO3 films. We ascribe this breakdown in the exchange coupling to a weakening of the antiferromagnetic order in the ultrathin BiFeO3 film based on our X-ray linear dichroism measurements. These observations are consistent with an interfacial exchange coupling between the CoFe moments and a canted antiferromagnetic moment in the BiFeO3.
@article{arxiv.1304.5394,
title = {Interfacial Coupling in Multiferroic-Ferromagnet Heterostructures},
author = {M. Trassin and J. D. Clarkson and S. R. Bowden and Jian Liu and J. T. Heron and R. J. Paull and E. Arenholz and D. T. Pierce and J. Unguris},
journal= {arXiv preprint arXiv:1304.5394},
year = {2013}
}