Controlling the Magneto-Optical Response in Ultrathin Films of EuO1- x via Interface Engineering with Ferroelectric BaTi2O5

Abstract

Utilizing pulsed laser deposition, a film of EuO_1-x was deposited onto a Si(001) substrate with MgO buffer and compared to the same heterostructure with an additional BaTi₂O₅ thin film on top of the EuO_1-x surface. X-ray diffraction (XRD) indicates the films crystallize into a preferred EuO(111) orientation; it also reveals the clear presence of EuSi_2, which suggests Si or Eu diffuses across the MgO buffer layer. EuO_1-x films exhibit a ferromagnetic (FM) signature and temperature-dependent exchange bias, indicated by MOKE measurements, suggesting the presence of a magnetic order well above the EuO Curie temperature with possible origins in charge carrier density near the interface. In comparison, an antiferromagnetic character persists well above the EuO Curie temperature of 69 K and the enhanced Curie temperature of 150 K for BaTi₂O₅ films grown on the EuO_1-x films. The antiferromagnetic behavior is not seen in thicker EuO_1-x thin films when integrated with other ferroelectric (FE) phases of the BaO-TiO₂ system, suggesting an origin in the perturbed charge population at the BaTi₂O₅/EuO_1-x interface.

Keywords: FM/AFM interface; bound magnetic polarons; exchange bias; magnetic semiconductor; orbital overlap; resonant tunneling; temperature-dependent exchange bias.