Image charge screening: a new approach to enhance magnetic ordering temperatures

TL;DR

This study demonstrates that image charge screening significantly enhances the magnetic ordering temperature in ultra-thin NiO films, suggesting a new method for designing strongly correlated oxide nanostructures with improved magnetic properties.

Contribution

The paper introduces the concept of using image charge screening to increase magnetic ordering temperatures in ultra-thin films, validated through experimental comparison of NiO on different substrates.

Findings

NiO film on Ag(100) has a Neel temperature of 390 K.

NiO film on MgO(100) has a Neel temperature below 40 K.

Screening by polarizable media can enhance magnetic properties.

Abstract

We have tested the concept of image charge screening as a new approach to enhance magnetic ordering temperatures and superexchange interactions in ultra thin films. Using a 3 monolayer NiO(100) film grown on Ag(100) and an identically thin film on MgO(100) as model systems, we observed that the Neel temperature of the NiO film on the highly polarizable metal substrate is 390 K while that of the film on the poorly polarizable insulator substrate is below 40 K. This demonstrates that screening by highly polarizable media may point to a practical way towards designing strongly correlated oxide nanostructures with greatly improved magnetic properties.