Anomalous exchange coupling in transition-metal-oxide based superlattices with antiferromagnetic spacer layers

TL;DR

This paper investigates the magnetic and electronic properties of SrMnO3/SrRuO3 superlattices, revealing a correlation between coercive field and magnetoresistance, driven by spin-polarized quantum tunneling influenced by spacer layer thickness.

Contribution

It demonstrates anomalous exchange coupling in transition-metal-oxide superlattices with antiferromagnetic layers, highlighting the role of quantum tunneling without mobile carriers.

Findings

Coercive field correlates with magnetoresistance in superlattices.

Magnetoresistance exhibits sharp jumps at coercive fields.

Oscillations in magnetic properties depend on spacer layer thickness.

Abstract

A direct correlation is seen between the coercive field (HC) and the magnetic-field-dependent resistivity (MR) in SrMnO3/SrRuO3 superlattices of perpendicular magnetic anisotropy. The magnetoresistance shows a sharp jump at Hc for in-plane current and the out-of-plane magnetic field. Both HC and high-field MR also oscillate with the thickness of the SrMnO3 spacer layers separating the metallic ruthenate. Since the spacer in these superlattices has no mobile carriers to facilitate an oscillatory coupling, we attribute the observed behavior to the spin-polarized quantum tunneling of electrons between the ferromagnetic layers and antiferromagnetically ordered t2g spins of SrMnO3.