The temperature dependence of exchange bias properties are studied in polycrystalline BiFeO3/Ni81Fe19 bilayers, for different BiFeO3 thicknesses. Using a field cooling protocol, a non-monotonic behavior of the exchange bias field is shown in the exchange-biased bilayers. Another thermal protocol, the Soeya protocol, related to the BiFeO3 thermal activation energies was carried out and reveals a two-step evolution of the exchange bias field. The results of these two different protocols are similar to the ones obtained for measurements previously reported on epitaxial BiFeO3, indicating a driving mechanism independent of the long-range crystalline arrangement (i.e., epitaxial or polycrystalline). An intrinsic property of BiFeO3 is proposed as being the driving mechanism for the thermal dependent magnetization reversal: the canting of the BiFeO3 spins leading to a biquadratic contribution to the exchange coupling. The temperature dependence of the magnetization reversal angular behavior agrees with the presence of such a biquadratic contribution for exchange biased bilayers studied here.
@article{arxiv.1608.00736,
title = {Temperature dependence of exchange biased multiferroic $ \mathbf{BiFeO_3} $/$ \mathbf{Ni_{81}Fe_{19}} $ polycrystalline bilayer},
author = {J. Richy and T. Hauguel and J. Ph. Jay and S. P. Pogossian and B. Warot-Fonrose and C. J. Sheppard and J. L. Snyman and A. M. Strydom and J. Ben Youssef and A. R. E. Prinsloo and D. Spenato and D. T. Dekadjevi},
journal= {arXiv preprint arXiv:1608.00736},
year = {2016}
}