Mechanism of ferromagnetism enhancement in a La$_{2/3}$ Sr$_{1/3}$ MnO$_3$ membrane released from epitaxial strain

TL;DR

This study reveals that releasing La$_{2/3}$ Sr$_{1/3}$ MnO$_3$ from its substrate enhances ferromagnetism by increasing electron itineracy and double-exchange interactions, elucidated through synchrotron radiation measurements.

Contribution

It provides a microscopic understanding of ferromagnetism enhancement in LSMO membranes by strain release, using resonant photoemission spectroscopy.

Findings

Strain release increases Mn-3d electron itineracy.

Enhanced p-d hybridization strengthens double-exchange.

Ferromagnetism improves due to reinforced double-exchange interaction.

Abstract

Recent studies have shown that the magnetic properties of the ferromagnetic perovskite oxide La$_{2/3}$ Sr$_{1/3}$ MnO$_3$ (LSMO) grown on an SrTiO3 (STO) substrate, such as its magnetic moment and Curie temperature, can be improved by releasing the film from the substrate. However, the microscopic origin of this enhancement is not yet well understood. In this study, we use synchrotron radiation measurements to investigate the mechanism of ferromagnetism enhancement in an LSMO membrane released from an STO substrate by dissolving a water-soluble Sr$_4$Al$_2$O$_7$ buffer layer. Using resonant photoemission spectroscopy on the as-grown LSMO film and LSMO membrane, we elucidate that the strain release from the STO substrate enhances the itineracy of the Mn-3d electrons via p-d hybridization, and this strengthens the double-exchange interaction. The reinforcement of the double-exchange interaction, in turn, improves the ferromagnetism of LSMO.