Temperature dependence of exchange biased multiferroic $ \mathbf{BiFeO_3} $/$ \mathbf{Ni_{81}Fe_{19}} $ polycrystalline bilayer

J. Richy; T. Hauguel; J. Ph. Jay; S. P. Pogossian; B. Warot-Fonrose; C. J. Sheppard; J. L. Snyman; A. M. Strydom; J. Ben Youssef; A. R. E. Prinsloo; D. Spenato; D. T. Dekadjevi

arXiv · 1608.00736

Temperature dependence of exchange biased multiferroic $ \mathbf{BiFeO_3} $/$ \mathbf{Ni_{81}Fe_{19}} $ polycrystalline bilayer

J. Richy·T. Hauguel·J. Ph. Jay·S. P. Pogossian·B. Warot-Fonrose·C. J. Sheppard·J. L. Snyman·A. M. Strydom·J. Ben Youssef·A. R. E. Prinsloo·D. Spenato·D. T. Dekadjevi

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Abstract

The temperature dependence of exchange bias properties are studied in polycrystalline $ \mathrm{BiFeO_3} / \mathrm{Ni_{81}Fe_{19}} $ bilayers, for different $ \mathrm{BiFeO_3} $ 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 $ \mathrm{BiFeO_3} $ 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 $ \mathrm{BiFeO_3} $, indicating a driving mechanism independent of the long-range crystalline arrangement (i.e., epitaxial or polycrystalline). An intrinsic property of $ \mathrm{BiFeO_3} $ is proposed as being the driving mechanism for the thermal dependent magnetization reversal: the canting of the $ \mathrm{BiFeO_3} $ 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.

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J. Richy, T. Hauguel, J. Ph. Jay, S. P. Pogossian, B. Warot-Fonrose, C. J. Sheppard, J. L. Snyman, A. M. Strydom, J. Ben Youssef, A. R. E. Prinsloo, D. Spenato, D. T. Dekadjevi. 2016-08-02. Temperature dependence of exchange biased multiferroic $ \mathbf{BiFeO_3} $/$ \mathbf{Ni_{81}Fe_{19}} $ polycrystalline bilayer. https://arxiv.org/abs/1608.00736

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