Reversal of Anomalous Hall Effect and Octahedral Tilting in SrRuO₃ Thin Films via Hydrogen Spillover

Abstract

The perovskite SrRuO3 (SRO) is a strongly correlated oxide whose physical and structural properties are strongly intertwined. Notably, SRO is an itinerant ferromagnet that exhibits a large anomalous Hall effect (AHE) whose sign can be readily modified. Here, a hydrogen spillover method is used to tailor the properties of SRO thin films via hydrogen incorporation. It is found that the magnetization and Curie temperature of the films are strongly reduced and, at the same time, the structure evolves from an orthorhombic to a tetragonal phase as the hydrogen content is increased up to ≈0.9 H per SRO formula unit. The structural phase transition is shown, via in situ crystal truncation rod measurements, to be related to tilting of the RuO6 octahedral units. The significant changes observed in magnetization are shown, via density functional theory (DFT), to be a consequence of shifts in the Fermi level. The reported findings provide new insights into the physical properties of SRO via tailoring its lattice symmetry and emergent physical phenomena via the hydrogen spillover technique.

Symmetry‐Controlled Sign Reversal and Anisotropy in Magnetoresistance of SrRuO3 Epitaxial Films

“…Note that the coercive fields of t SRO ‐dependent hysteresis MR exhibit a consistent change with the evolution of isotropic AHE along SRO O [10] (Figure 1d–i) and SRO O [001] (Figure S3, Supporting Information) without sign reversal (Figure S4, Supporting Information). The sign reversal of AHE in SRO generally arises from the changes in either band structure or the Fermi level position, which can be triggered by various factors such as film thickness, [ 41–43 ] temperature, [ 19,44,45 ] hydrogenation. [ 44 ] However, based on the experimental results, none of these factors influences our samples at 10 K. The sign reversal of MR appears only on the nonhysteresis component.…”

“…The sign reversal of AHE in SRO generally arises from the changes in either band structure or the Fermi level position, which can be triggered by various factors such as film thickness, [41][42][43] temperature, [19,44,45] hydrogenation. [44] However, based on the experimental results, none of these factors influences our samples at 10 K. The sign reversal of MR appears only on the nonhysteresis component. It is obvious that the enhancement of MR anisotropy (Figure 3j) and the tetragonal-to-orthorhombic structural phase transition (Figure 2) occurs at a similar t SRO range.…”

Adsorption-Controlled Growth and Magnetism in Epitaxial SrRuO3 Films

“…In contrast, all the films within the growth window showed a stepped feature (circled in Figure a for T Ru = 178 °C). Within a two-domain picture, reports ,,− interpret both the hump-like feature and the stepped feature in the observed anomalous Hall curves as an outcome of the superposition of the anomalous Hall curves from two magnetic domains of coercivities H c,1 and H c,2 (< H c,1 ), illustrated schematically in Figure b. We extract the coercivities H c,1 and H c,2 from the peaks in the field derivative of the anomalous Hall resistance (d R xy AHE /d H ) (Figure S3, Supporting Information).…”

“…Some studies argue that the hump-like features arise from the topological Hall effect, − a manifestation of the enhanced Hall signal produced when the conduction electrons in SrRuO 3 interact with the skyrmion-produced magnetic field. Other studies contest this argument, suggesting that these features are associated with multiple magnetic domains that arise from inhomogeneities in film thickness, Ru deficiency, the presence of different structural domains, or the stabilization of multiple crystal polymorphs of SrRuO 3 . − Additional factors such as epitaxial strain-induced changes to the Berry phase curvature and proton intercalation into the SrRuO 3 lattice through ionic gating can produce changes in the anomalous Hall resistance and complicate this analysis. These observations highlight the intimate relationship among the structural, electrical, and magnetic properties of SrRuO 3 .…”

Suppression of Oxygen Vacancies in Rutile Ruo2 via In Situ Exsolution for Enhanced Water Electrocatalysis

“…[19] It is worth mentioning that RuO 2 and SrRuO 3 have the similar structure with Ru inside the oxygen octahedral cage, thus we will not distinguish them because of the small difference. [36,37]…”