A. Solignac, R. Guerrero, P. Gogol, T. Maroutian, F. Ott, L. Largeau, Ph. Lecoeur, and M. Pannetier-Lecoeur
Phys. Rev. Lett. 109 (2012) 027201.
We have studied the magnetic hysteresis cycle of La0;67Sr0.33MnO3/SrRuO3 antiferromagnetically coupled bilayers, by magnetometry and polarized neutron reflectometry. A positive exchange bias as well as an unusual asymmetry are observed on the magnetic reversal process of the La0;67Sr0.33MnO3 layer. Through an extended Stoner-Wohlfarth model comprising the magnetic anisotropy of both layers, we give experimental evidence that this asymmetry originates from two different but well-defined antiferromagnetic coupling strengths at the interface between the two magnetic oxides. The possible origin of this dual coupling is discussed in view of our experimental results.