Novel types of magnetic order generated across epitaxial interfaces of 4d and 5d transition metal perovskite oxides
Final Report Abstract
A means to tailor physical properties of matter is to design artificial structures such as epitaxial heterostructures, in which structural accommodations and interfacial coupling occur, which, together with the broken inversion symmetry, strongly influence the physical properties of the heterostructures, often resulting in novel properties. Here we addressed the particular case of epitaxial multilayers built up by interfacing layers of SrRuO3 - a 4d oxide ferromagnet - with layers of the large spin-orbit coupling paramagnetic SrIrO3 and insulating isostructural perovskite oxides such as SrHfO3 and SrZrO3. Multilayers with asymmetric and symmetric interfaces for the ferromagnetic SrRuO3 layers were studied with the expectation that generation of a net interfacial Dzyaloshinskii-Moriya interaction (DMI) is possible in the asymmetric geometry and less favourable in the symmetric geometry. Unlike the metallic multilayers, such as Pt/Co/Ir, where the interfacial DMI is well established and the magnetic interlayer coupling across the non-magnetic spacers can be ferromagnetic, for the perovskite oxide epitaxial multilayers both the interfacial DMI and the interlayer coupling are not yet understood and much less studied. For example, here we demonstrated that ferromagnetic SrRuO3 layers, separated by spacers of SrIrO3/SrZrO3 so thin as 2 monolayers have only a very weak ferromagnetic coupling at all temperatures down to 10 K. The lack of magnetic coupling makes the imaging of the magnetic domains in these multilayers, both by magnetic force microscopy and Lorentz transmission electron microscopy (LTEM), very difficult and thus no information about the chiral behaviour of the domains or possible formation of skyrmions could be inferred. Additionally, LTEM requires special preparation of specimens from the epitaxial multilayers and this turned out to be very challenging for materials sensitive to ion beam irradiation. A technically simple way of probing the formation of skyrmions is to measure the topological Hall resistivity that should occur in the presence of skyrmions as an additional contribution to the ordinary and anomalous Hall effect (AHE). This type of probing relies on the assumption that the topological Hall effect contribution can be extracted unambiguously from the measured total Hall resistivity. Humplike anomalies of the Hall effect resistance loops were often attributed to the formation of skyrmions. Our studies revealed that the detection of skyrmions solely by Hall effect measurements can be misleading in the case of SrRuO3 heterostructures, as the AHE itself has a complex magnetization dependence and is highly sensitive to minute structural and electronic properties variations.
Publications
- Hall effect of asymmetric La0.7Sr0.3MnO3/SrTiO3/SrRuO3 and La0.7Sr0.3MnO3/BaTiO3/SrRuO3 superlattices, Journal of Applied Physics 124, 163905 (2018)
M. Ziese and I. Lindfors-Vrejoiu
(See online at https://doi.org/10.1063/1.5051812) - Magnetic interlayer coupling between epitaxial SrRuO3 layers separated by ultrathin non-magnetic SrIrO3/SrZrO3, Appl. Phys. Let. 113, 192402 (2018)
Lena Wysocki, Ramil Mirzaaghayev, Michael Ziese, Lin Yang, Jörg Schöpf, Rolf B. Versteeg, Andrea Bliesener, Johannes Engelmayer, András Kovács, Lei Jin, Felix Gunkel, Regina Dittmann, Paul H. M. van Loosdrecht, and Ionela Lindfors-Vrejoiu
(See online at https://doi.org/10.1063/1.5050346) - Topological Signatures in the Hall Effect of SrRuO3/ La0.7Sr0.3MnO3 SLs, Phys. Status Solidi B 1900628, (2019)
Michael Ziese, Francis Bern, Pablo D. Esquinazi, and Ionela Lindfors-Vrejoiu
(See online at https://doi.org/10.1002/pssb.201900628) - Unconventional anomalous Hall effect driven by the oxygen-octahedra-tailoring of the SrRuO3 structure, J. Phys. Mater. 2, 034008 (2019)
M. Ziese, L. Jin and I. Lindfors-Vrejoiu
(See online at https://doi.org/10.1088/2515-7639/ab1aef) - Correlating the nanoscale structural, magnetic, and magneto-transport properties in SrRuO3-based Perovskite Thin films: Implications for oxide skyrmion devices, ACS Applied Nano Materials 3, 2, 1182–1190 (2020)
G. Malsch, D. Ivaneyko, P. Milde, L. Wysocki, L. Yang, P. H. M. van Loosdrecht, I. Lindfors-Vrejoiu, and L. M. Eng
(See online at https://doi.org/10.1021/acsanm.9b01918) - Electronic Inhomogeneity Influence on the Anomalous Hall Resistivity Loops of SrRuO3 Epitaxially Interfaced with 5d Perovskites, ACS Omega 5, 11, 5824–5833, 2020
Lena Wysocki, Jörg Schöpf, Michael Ziese, András Kovács, Lei Jin, Rolf B. Versteeg, Andrea Bliesener, Felix Gunkel, Lior Kornblum, Regina Dittmann, Paul H. M. van Loosdrecht, and Ionela Lindfors-Vrejoiu
(See online at https://doi.org/10.1021/acsomega.9b03996) - Origin of the hump anomalies in the Hall resistance loops of ultrathin SrRuO3/SrIrO3 multilayers
Lin Yang, Lena Wysocki, Jörg Schöpf, Lei Jin, András Kovács, Felix Gunkel, Regina Dittmann, Paul H. M. van Loosdrecht, and Ionela Lindfors-Vrejoiu
- Validity of magnetotransport detection of skyrmions in epitaxial SrRuO3 heterostructures, Phys. Rev. Materials 4, 054402 (2020)
Lena Wysocki, Yang Lin, Felix Gunkel, Regina Dittmann, Paul H. M. van Loosdrecht, and Ionela Lindfors-Vrejoiu
(See online at https://doi.org/10.1103/physrevmaterials.4.054402)
