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Functional oxides exhibit diverse useful properties, opening attractive prospects for electronic, magnetic, and optoelectronic devices. However, the chemical instability of these oxides with some microfabrication processes, especially when dealing with thin films (<40 nm) or micrometer-scale lateral dimensions, can pose a considerable challenge. Here, we describe the fabrication process of a Hall bar device used as a test structure for thin functional oxide films. This process employs photolithography and dry etching, utilizing standard clean-room materials and methods. The device layout and fabrication process are described in detail, including conclusions and lessons gained from several failed attempts during process development. A key lesson is the advantage of employing an ultrathin protective layer to protect the oxide film surface. In addition, we encountered two additional fabrication challenges: photoresist hardening during dry etching and edge accumulation of photoresist during spin-coating. Effective solutions to these issues are described. We hope that our lessons and conclusions, not limited to functional oxides, will help to shorten the process development for other materials and devices. [ABSTRACT FROM AUTHOR]

Ferromagnetic multilayers with asymmetric interfaces and perpendicular magnetic anisotropy can stabilize non-trivial magnetic structures due to interfacial Dzyaloshinskii-Moriya interactions. Magnetic interlayer coupling between ferromagnetic layers separated by non-magnetic insulating spacers is an additional important ingredient for the properties of multilayers. We addressed the magnetic coupling between ferromagnetic SrRuO3 epitaxial layers separated by ultrathin spacers of SrIrO3/SrZrO3, so that inversion symmetry is broken at the top and bottom interfaces. Major and minor magnetization loops allowed us to assess the type and strength of the magnetic coupling. We inferred that the magnetic coupling of SrRuO3 layers through non-magnetic insulating interlayers (≤1.6 nm thick) is weakly ferromagnetic. [ABSTRACT FROM AUTHOR]

Ferromagnetic multilayers with asymmetric interfaces and perpendicular magnetic anisotropy can stabilize non-trivial magnetic structures due to interfacial Dzyaloshinskii-Moriya interactions. Magnetic interlayer coupling between ferromagnetic layers separated by non-magnetic insulating spacers is an additional important ingredient for the properties of multilayers. We addressed the magnetic coupling between ferromagnetic SrRuO3 epitaxial layers separated by ultrathin spacers of SrIrO3/SrZrO3, so that inversion symmetry is broken at the top and bottom interfaces. Major and minor magnetization loops allowed us to assess the type and strength of the magnetic coupling. We inferred that the magnetic coupling of SrRuO3 layers through non-magnetic insulating interlayers (≤1.6 nm thick) is weakly ferromagnetic. [ABSTRACT FROM AUTHOR]

Ferromagnetic La 0.7 Sr 0.3 Mn 1- x Ru x O 3 epitaxial multilayers with controlled variation of the Ru/Mn content were synthesized to engineer canted magnetic anisotropy and variable exchange interactions, and to explore the possibility of generating a Dzyaloshinskii-Moriya interaction. The ultimate aim of the multilayer design is to provide the conditions for the formation of domains with nontrivial magnetic topology in an oxide thin film system. Employing magnetic force microscopy and Lorentz transmission electron microscopy in varying perpendicular magnetic fields, magnetic stripe domains separated by Néel-type domain walls as well as Néel skyrmions smaller than 100 nm in diameter were observed. These findings are consistent with micromagnetic modeling, taking into account a sizable Dzyaloshinskii-Moriya interaction arising from the inversion symmetry breaking and possibly from strain effects in the multilayer system.

SrRuO 3 , a 4d ferromagnet with multiple Weyl nodes at the Fermi level, offers a rich playground to design epitaxial heterostructures and superlattices with fascinating magnetic and magnetotransport properties. Interfacing ultrathin SrRuO 3 layers with large spin-orbit coupling 5d transition-metal oxides, such as SrIrO 3 , results in pronounced peaklike anomalies in the magnetic field dependence of the Hall resistivity. Such anomalies have been attributed either to the formation of Néel-type skyrmions or to modifications of the Berry curvature of the topologically nontrivial conduction bands near the Fermi level of SrRuO 3 . Here, epitaxial multilayers based on SrRuO 3 interfaced with 5d perovskite oxides, such as SrIrO 3 and SrHfO 3 , were studied. This work focuses on the magnetotransport properties of the multilayers, aiming to unravel the role played by the interfaces with 5d perovskites in the peaklike anomalies of the Hall resistance loops of SrRuO 3 layers. Interfacing with large band gap insulating SrHfO 3 layers did not influence the anomalous Hall resistance loops, while interfacing with the nominally paramagnetic semimetal SrIrO 3 resulted in pronounced peaklike anomalies, which have been lately attributed to a topological Hall effect contribution as a result of skyrmions. This interpretation is, however, under strong debate and lately alternative causes, such as inhomogeneity of the thickness and the electronic properties of the SrRuO 3 layers, have been considered. Aligned with these latter proposals, our findings reveal the central role played in the anomalies of the Hall resistivity loops by electronic inhomogeneity of SrRuO 3 layers due to the interfacing with semimetallic 5d 5 SrIrO 3 ., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)