Interfacial oxygen-octahedral-tilting-driven electrically tunable topological Hall effect in ultrathin SrRuO₃ films

Abstract

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.

Reversible manipulation of the magnetic state in SrRuO3 through electric-field controlled proton evolution

“…Recently, there are also emerging research interests in SrRuO 3 system on its exotic topological spin texture with the reports of the topological Hall effect (THE), which is attributed to the inequivalent interfaces in the studied ultra-thin films 11,13,[16][17][18][19][20] . Furthermore, some recent results demonstrated nicely the electric-field controlled THE in ultrathin SrRuO 3 films through the dielectric and ferroelectric modulations 11,13 , although the resultant effect remains subtle, reminiscent of its electric-field controlled magnetic state.…”

Coupling Charge and Topological Reconstructions at Polar Oxide Interfaces

“…In this sense, the system considered here offers a pleasing simplicity and a more direct approach toward controlling the topology in ultrathin SrRuO 3 and potentially other correlated metals. Our results are also of relevance to the scenario of uncapped SrRuO 3 films [83], where dangling bonds at the surface can manifest as a charged electrostatic boundary condition [38], albeit complicated by the unavoidable interaction with adsorbed ambient chemical species.…”

Noncollinear spintronics and electric-field control: a review

“…It is indeed rather promising to combine noncollinear spintronic materials with an ultrathin ferroelectric oxide thin film to build a complex magnetic/ferroelectric/magnetic heterostructure, which could enable the electric-field control of the tunnel magnetoresistance via either ferroelectric polarization switching [62] or oxygen manipulation [63,64]. Despite of the fact that most of well-studied noncollinear magnetic materials are intermetallic alloys, it is possible to realize the exotic noncollinear spin order in ultrathin magnetic oxide systems such as LaMnO3 [65,66] or SrRuO3 [67] through multiple possible approaches, for example, oxygen octahedral tilting [68,69], direct [70] or long-range [71] exchange coupling, and inversion symmetry break by interfacing a heavy metal [72], which could further become free standing by using a water-dissolvable Sr3Al2O6 buffer layer [73] and thus facilitate the transfer of noncollinear oxide based spintronic devices onto silicon.…”