Temperature dependence of exchange biased multiferroic BiFeO 3 /Ni 81 Fe 19 polycrystalline bilayer

J. Richy (1) , T. Hauguel (1) , Jean-Philippe Jay (2) , S. Pogossian (1) , Bénédicte Warot-Fonrose (3) , J Sheppard (4) , J Snyman (4) , A Strydom (4) , J Ben Youssef (5) , A Prinsloo (4) , D. Spenato (2) , D. Dekadjevi (1)

1 LMB - Laboratoire de magnétisme de Bretagne
2 OPTIMAG - Laboratoire d'Optique et de Magnétisme
3 CEMES-I3EM - Interférométrie, In situ et Instrumentation pour la Microscopie Electronique
4 UJ - University of Johannesburg [South Africa]
5 Lab-STICC - Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance

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

Domaines: Science des matériaux [cond-mat.mtrl-sci]

J. Richy, T. Hauguel, Jean-Philippe Jay, S. Pogossian, Bénédicte Warot-Fonrose, et al.. Temperature dependence of exchange biased multiferroic BiFeO 3 /Ni 81 Fe 19 polycrystalline bilayer. Journal of Physics D: Applied Physics, 2018, 51 (12), pp.125308. ⟨10.1088/1361-6463/aab023⟩. ⟨hal-01735729⟩