Topological spin textures as an emerging class of topological matter offer a medium for information storage and processing. The recently discovered topological Hall effect (THE) is considered as a fingerprint for electrically probing non-trivial spin-textures. But the origin of THE in oxides has remained elusive. Here we report an observation of the THE in ultrathin ( 8 unit cells. u.c.) 4d ferromagnetic SrRuO 3 films grown on SrTiO 3 (001) substrates, which can be attributed to the chiral ordering of spin structure (i.e., skyrmion-like) in the single SrRuO 3 layer without contacting 5d oxide SrIrO 3 layer. It is revealed that the RuO 6 octahedral tilting induced by local orthorhombic-to-tetragonal structural phase transition exists across the SrRuO 3 /SrTiO 3 interface, which naturally breaks the inversion symmetry. Our theoretical calculations demonstrate that the Dzyaloshinskii-Moriya (DM) interaction arises owing to the broken inversion symmetry and strong spin-orbit interaction of 4d SrRuO 3 . This DM interaction can stabilize the Né el-type magnetic skyrmions, which in turn accounts for the observed THE in transport. The RuO 6 octahedral tilting-induced DM interaction provides a pathway toward the electrical control of the topological spin textures and resultant THE, which is confirmed both experimentally and theoretically. Besides the fundamental significance, the 3 understanding of THE in oxides and its electrical manipulation presented in this work could advance the low power cost topological electronic and spintronic applications.
Manipulation of oxygen vacancies (V O ) in single oxide layers by varying the electric field can result in significant modulation of the ground state. However, in many oxide multilayers with strong application potentials, e.g. ferroelectric tunnel junctions and solid-oxide fuel cells, understanding V O behaviour in various layers under an applied electric field remains a challenge, owing to complex V O transport between different layers. By sweeping the external voltage, a reversible manipulation of V O and a corresponding fixed magnetic phase transition sequence in cobaltite/manganite (SrCoO 3-x /La 0.45 Sr 0.55 MnO 3-y ) heterostructures are reported. *The magnetic phase transition sequence confirms that the priority of electric-field-induced V O formation/annihilation in the complex bilayer system is mainly determined by the V O formation energies and Gibbs free energy differences, which is supported by theoretical analysis. We not only realize a reversible manipulation of the magnetic phase transition in an oxide bilayer, but also provide insight into the electric field control of V O engineering in heterostructures.
SrFeO x (SFO x ) compounds exhibit ionic conduction and oxygen-related phase transformation, having potential applications in solid oxide fuel cells, smart windows, and memristive devices. The phase transformation in SFO x typically requires a thermal annealing process under various pressure conditions, hindering their practical applications. Here, we have achieved a reversible phase transition from brownmillerite (BM) to perovskite (PV) in SrFeO2.5 (SFO2.5) films through ionic liquid (IL) gating. The real-time phase transformation is imaged using in situ high-resolution transmission electron microscopy. The magnetic transition in SFO2.5 is identified by fabricating an assisted La0.7Sr0.3MnO3 (LSMO) bottom layer. The IL-gating-converted PV phase of a SrFeO3−δ (SFO3−δ) layer shows a ferromagnetic-like behavior but applies a huge pinning effect on LSMO magnetic moments, which consequently leads to a prominent exchange bias phenomenon, suggesting an uncompensated helical magnetic structure of SFO3−δ. On the other hand, the suppression of both magnetic and exchange coupling signals for a BM-phased SFO2.5 layer elucidates its fully compensated G-type antiferromagnetic nature. We also demonstrated that the phase transition by IL gating is an effective pathway to tune the resistive switching parameters, such as set, reset, and high/low-resistance ratio in SFO2.5-based resistive random-access memory devices.
Antiferromagnets with zero net magnetic moment, strong anti-interference and ultrafast switching speed have potential competitiveness in high-density information storage. Body centered tetragonal antiferromagnet Mn 2 Au with opposite spin sub-lattices is a unique metallic material for Néel-order spin-orbit torque (SOT) switching. Here we investigate the SOT switching in quasi-epitaxial (103), (101) and (204) Mn 2 Au films prepared by a simple magnetron sputtering method. We demonstrate current induced antiferromagnetic moment switching in all the prepared Mn 2 Au films by a short current pulse at room temperature, whereas different orientated films exhibit distinguished switching characters. A directionindependent reversible switching is attained in Mn 2 Au (103) films due to negligible magnetocrystalline anisotropy energy, while for Mn 2 Au (101) and (204) films, the switching is invertible with the current applied along the in-plane easy axis and its vertical axis, but becomes attenuated seriously during initially switching circles when the current is applied along hard axis, because of the existence of magnetocrystalline anisotropy energy. Besides the fundamental significance, the strong orientation dependent SOT switching, which was not realized irrespective of ferromagnet and antiferromagnet, provides versatility for spintronics. *
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