Anisotropy-driven interfacial magnetism in Ru-deficient SrRuO$_3$ thin films

TL;DR

This study demonstrates that Ru deficiency in SrRuO$_3$ thin films significantly influences their electronic and magnetic properties, especially at interfaces, enabling tailored interfacial magnetism through defect engineering.

Contribution

It reveals how Ru deficiency affects transport and magnetic anisotropy in SrRuO$_3$ thin films, highlighting defect and interface engineering as tools to control interfacial magnetism.

Findings

Ru deficiency suppresses electronic transport and reduces saturation magnetization.

Interfacial regions remain ferromagnetic with enhanced perpendicular magnetic anisotropy.

Curie temperature remains largely unaffected by Ru deficiency.

Abstract

While stoichiometric SrRuO$_3$ (SRO) is a metallic itinerant ferromagnet with relatively homogeneous magnetization, Ru deficiency provides a powerful route to alter its electronic transport and depth-dependent magnetic properties. Ru-deficient SRO thin films grown by radio-frequency high oxygen pressure sputtering were investigated using a combination of X-ray reflectivity, polarized neutron reflectometry, off-specular neutron scattering, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy, electrical transport, and magnetometry. Structural and compositional analyses reveal that Ru deficiency is intrinsic to the films, with an enhanced deficiency at the interfaces. As a result, coherent electronic transport is suppressed and the saturation magnetization is reduced, while the Curie temperature remains largely unaffected, placing Ru-deficient SRO in a regime consistent with ferromagnetic insulator-like behavior. Depth- and lateral-resolved magnetic measurements further show that the interfacial regions remain ferromagnetic but exhibit enhanced perpendicular magnetic anisotropy, which constrains the local magnetization to remain predominantly out-of-plane and strongly reduces its in-plane projection. Our results establish Ru deficiency as a key control parameter governing transport, magnetization, and anisotropy in SRO thin films and highlight defect and interface engineering as powerful routes to tailor interfacial magnetism in correlated oxide heterostructures.