Unconventional exchange bias coupling at perovskite/brownmillerite interface in spontaneously stabilized SrCoO3-{\delta}/SrCoO2.5 bi-layer

TL;DR

This study reveals an unconventional exchange bias effect at the interface of SrCoO3-{ extdelta} and SrCoO2.5 bi-layers, advancing understanding of interfacial magnetism in complex oxide heterostructures.

Contribution

It demonstrates a novel magnetic exchange bias phenomenon at a perovskite/brownmillerite interface without cation modification, expanding the scope of interfacial magnetic control.

Findings

Unconventional exchange bias observed at the interface.

Finite coercive field in the paramagnetic state.

Effect attributed to interfacial ferromagnet/antiferromagnet coupling.

Abstract

Interface effect in complex oxide thin film heterostructures lies at the vanguard of current research to design technologically relevant functionality and explore emergent physical phenomena. While most of the previous works focus on the perovskite/perovskite heterostructures, the study on perovskite/brownmillerite interfaces remain at its infancy. Here, we investigate spontaneously stabilized perovskite-ferromagnet (SrCoO3-{\delta})/brownmillertite-antiferromagnet (SrCoO2.5) bi-layer with TN > TC and discover an unconventional interfacial magnetic exchange bias effect. From magnetometry investigations, it is rationalized that the observed effect stems from the interfacial ferromagnet/antiferromagnet coupling. The possibility for coupled ferromagnet/spinglass interface engendering such effect is ruled out. Strikingly, a finite coercive field persists in the paramagnetic state of SrCoO3-{\delta} whereas the exchange bias field vanishes at TC. We conjecture the observed effect to be due to the effective external quenched staggered field provided by the antiferromagtic layer for the ferromagnetic spins at the interface. Our results not only unveil a new paradigm to tailor the interfacial magnetic properties in oxide heterostructures without altering the cations at the interface, but also provide a purview to delve into the fundamental aspects of exchange bias in such unusual systems paving a big step forward in thin film magnetism.