No abstract

The study of interfacial Dzyaloshinskii-Moria interaction (DMI) in perpendicularly magnetized structurally asymmetric heavy metal /ferromagnet multilayer systems is of high importance due to the formation of chiral magnetic textures in the presence of DMI. Here, we report the impact of cobalt oxidation at the Co/AlOx interface in Pt/Co/AlOx trilayer structures on the DMI by varying the post-growth annealing time, Al thickness and substrate. To quantify DMI we employed magneto-optical imaging of the asymmetric domain wall expansion, hysteresis loop shift, and spin-wave spectroscopy techniques. We further correlated the Co oxidation with low-temperature Hall effect measurements and X-ray photoelectron spectroscopy. Our results emphasize the importance of full characterization of the magnetic films that could be used for magnetic random access memory technologies when subjected to the semiconductor temperature processing conditions, as the magnetic interactions are critical for device performance and can be highly sensitive to oxidation and other effects.

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.