Temperature dependence of the exchange bias properties in polycrystalline BiFeO3 /Ni80 Fe20
Résumé
In this study, we report a temperature dependent analysis of the exchange bias properties in BFO/Py bilayers as a function of the BFO thickness. The temperature dependence of the exchange bias field (He) and the coercive field (Hc) are first presented. To understand exchange bias magnetization reversal and the magnetic anisotropies, we will then present an azimuthal study of He and Hc at 300 K and 77 K. Finally, results of a controlled field cooling protocol applied on all samples will be discussed to understand anisotropy energy distribution. The bilayers were grown by radio-frequency sputter deposition, with the following structure: Si/Pt(14 nm)/BiFeO3(tBFO)/Ni80Fe20(10 nm)/ Pt(10 nm), with tBFO among 0 nm, 29 nm and 177 nm . To induce uniaxial anisotropy, a 300 Oe field Hdep was applied during the growth . The XRD analysis confirmed a single polycrystalline structure for the BFO layer.