Oxygen defects and
their atomic arrangements play a significant
role in the physical properties of many transition metal oxides. The
exemplary perovskite SrCoO
3-δ
(
P-
SCO) is metallic and ferromagnetic. However, its daughter phase,
the brownmillerite SrCoO
2.5
(
BM-
SCO),
is insulating and an antiferromagnet. Moreover,
BM-
SCO exhibits oxygen vacancy channels (OVCs) that in thin films can
be oriented either horizontally (
H
-SCO) or vertically
(
V
-SCO) to the film’s surface. To date, the
orientation of these OVCs has been manipulated by control of the thin
film deposition parameters or by using a substrate-induced strain.
Here, we present a method to electrically control the OVC ordering
in thin layers via ionic liquid gating (ILG). We show that
H
-SCO (antiferromagnetic insulator, AFI) can be converted
to
P
-SCO (ferromagnetic metal, FM) and subsequently
to
V
-SCO (AFI) by the insertion and subtraction of
oxygen throughout thick films via ILG. Moreover, these processes are
independent of substrate-induced strain which favors formation of
H
-SCO in the as-deposited film. The electric-field control
of the OVC channels is a path toward the creation of oxitronic devices.
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.
SrRuO3 Thin Films
The perovskite SrRuO3 is a prototypical itinerant ferromagnet that has drawn considerable attention due to its strongly correlated physical properties. In article number 2207246, Hyeon Han, Stuart S. P. Parkin, and co‐workers use the hydrogen spillover technique to modify the structure and magnetic properties and induce a reversal in sign of the anomalous Hall effect in SrRuO3 thin films, as revealed by comprehensive in situ experiments and density functional theory calculations.
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