Observation of Fe/BaTiO3 Interface State by X-Ray Absorption Spectroscopy

摘要

Electric field-induced change of magnetic properties in ferromagnetic Fe thin film grown on a ferroelectric BaTiO3 (BTO) substrate is studied by means of x-ray absorption spectroscopy. We find that a few nm Fe oxide layer exists at the Fe/BTO interface when the Fe thickness is 8 nm, in which the film shows in-plane magnetization. The x-ray magnetic circular dichroism analysis reveals that the coercive field, Hc, of Fe shows a hysteresis behavior as a function of the electric field, and larger Hc is observed at ∼ ±3 kV/cm. On the other hand, it is found from the extended x-ray absorption fine structure analysis that the Fe-O bond distance shows a similar electric field dependence to that of Hc, and shorter distance is observed at ∼ ±3 kV/cm. Therefore, it is assumed that the Hc strongly depends on the ferroelectric domain structure of BTO, and larger Hc is observed for the multi-domain structure. We suppose that shrinking of the Fe–O distance caused by the domain formation leads to an enhancement of Hc due to the island-like localization of the interface Fe oxide. [DOI: 10.1380/ejssnt.2015.139]