Image charge screening: A new approach to enhance magnetic ordering temperatures inultrathin correlated oxide films

We have tested the concept of image charge screening as a new approach to restore magnetic orderingtemperatures and superexchange interactions in correlated oxide ultrathin films. Using a three-monolayerNiO100 film grown on Ag100 and an identically thin film on MgO100 as model systems, we observedthat the Néel temperature of the NiO film on the highly polarizable metal substrate is 390 K while that of thefilm on the poorly polarizable insulator substrate is below 40 K. This demonstrates that screening by highlypolarizable media may point to a practical way toward designing strongly correlated oxide nanostructures withgreatly improved magnetic properties.