Controlling the Magneto-Optical Response in Ultrathin Films of EuO 1- x via Interface Engineering with Ferroelectric BaTi 2 O 5 .

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 BaTi 2 O 5 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 BaTi 2 O 5 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-TiO 2 system, suggesting an origin in the perturbed charge population at the BaTi 2 O 5 /EuO 1- x interface.