Induced ferromagnetic moment at the interface between epitaxial SrRuO$_3$ film and Sr$_2$RuO$_4$ single crystal

TL;DR

This study reveals an induced ferromagnetic moment at the interface between epitaxial SrRuO$_3$ films and Sr$_2$RuO$_4$ single crystals, suggesting new magnetic functionalities and phenomena in magnetic ruthenates.

Contribution

It demonstrates that the enhanced magnetization is specific to SRO113/SRO214 interfaces and is not due to strain or metallicity, indicating an interface-induced magnetic moment.

Findings

Enhanced magnetization occurs only at SRO113/SRO214 interface.

Strain and substrate metallicity do not influence the magnetization enhancement.

Magnetic moment induction extends over 20 nm into the SRO214 substrate.

Abstract

SrRuO$_3$ (SRO113) is an important material for device physics particularly as one of the best metallic oxide electrodes for ferroelectric devices. This oxide has moderate electron correlations with novel properties including ferromagnetic ordering, which can be utilized in future to spintronics and superconducting spintronics devices. Recently, we observed strongly enhanced magnetization of SRO113 thin films grown on single crystals of the spin-triplet superconductor Sr$_2$RuO$_4$ (SRO214). To clarify the origin of such an enhancement, we conducted systematic investigations of magnetic properties of SRO113 films deposited on a variety of oxide substrates. We carefully subtracted the substrate contributions and found that the enhanced 2 magnetization occurs only for SRO113/SRO214 films. We further found that neither strain nor metallicity of the substrate plays any significant roles in the enhancement. The X-ray magnetic circular dichroism reveals that the substrate-induced strain does not switch the Ru4+ state from the low-spin to high-spin states. The film-thickness dependence of the magnetization of SRO113/SRO214 films strongly suggest that the additional magnetization arises due to the induction of magnetic moment into the SRO214 substrate over 20-nm depth. Our results imply new magnetic functionality that can trigger studies searching for yet unknown physical phenomena in magnetic ruthenates.