Low-field switching of non-collinear spin textures at La0.7Sr0.3MnO3-SrRuO3 interfaces

K. Dörr, ¹* S. Das,¹ S. Agrestini,^3,4 A. D. Rata,¹ A. Herklotz,¹ I. Maznichenko,¹ A. Ernst,² I. Mertig, ^1,2 H. Babu Vasili, ⁴ S. M. Valvidares⁴

¹ Institute of Physics, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
² Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
³ Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
⁴ ALBA Synchrotron Light Source, E-08290 Cerdanyola del Vallès, Barcelona, Spain
*kathrin.doerr@physik.uni-halle.de

Magnetic coupling across interfaces is vitally important for spintronics. For example, it governs the spin polarization in tunnel junctions and the exchange bias used to pin the magnetization of single layers. Beyond that, engineering interfacial magnetism opens pathways to topologically non-trivial spin textures, as demonstrated for Skyrmions in metallic heterostructures. Interfaces of complex magnetic oxides are yet much less investigated regarding potential driving mechanisms for non-collinear magnetic structures than those in metals. Due to the intimate links between lattice and electronic degrees of freedom in transition metal oxides, novel types of chiral spin textures and alternative tools for tuning them can be expected. I discuss an apparently simple case of coherent interfaces between two prototype oxide ferromagnets, SrRuO₃ and La_0.7Sr_0.3MnO₃. Non-collinear interfacial magnetic textures have been derived from X-ray magnetic circular dichroism (XMCD) and magnetization measurements. The interfacial magnetic order and switching is fundamentally different for bilayers coherently grown in reversed stacking sequence. The SrRuO₃ top layer forms a persistent exchange spring which is antiferromagnetically coupled to La_0.7Sr_0.3MnO₃ and drives switching in fields of few mT. Density functional theory reveals crucial impact of the interface termination on the strength of Mn-Ru exchange coupling across the interface. The observation of an exchange spring agrees with ultrastrong coupling for the MnO₂ termination. Our results demonstrate low-field switching of non-collinear spin textures at interfaces between conducting oxides, providing access to studying and utilization of electron transport phenomena in such spin textures.