Possible High TC Layered Ferromagnetic Insulator Sr2NiRuO4: An ab initio Study

TL;DR

This study predicts that Sr2NiRuO4 is a promising layered ferromagnetic insulator with a high Curie temperature of 240 K, using ab initio calculations and Monte Carlo simulations, highlighting its potential for spintronic applications.

Contribution

The paper introduces a novel layered ferromagnetic insulator Sr2NiRuO4 with a high Curie temperature, based on combined theoretical methods, which is rare among such materials.

Findings

Sr2NiRuO4 exhibits strong ferromagnetic coupling.

Curie temperature estimated at 240 K.

Unique charge-spin-orbital configuration stabilizes ferromagnetism.

Abstract

Magnetic insulators are often antiferromagnetic (AFM) and layered AFM compounds usually show low ordering temperature. On the other hand, layered ferromagnetic (FM) insulators with high-TC are very rare although they could be quite useful for spintronic applications. Here, using crystal field level analysis in combination with density functional theory calculations as well as Monte Carlo simulations, we predict that the layered insulator Sr2NiRuO4 would have a strong FM coupling with TC as high as 240 K. The tetragonal crystal field in the Ni-O-Ru square plane stabilizes the S=1/2 Ni+ and S=3/2 Ru3+ states. The unique level ordering and occupation optimize the FM Ni-Ru superexchange interactions in the checkerboard arrangement, thus suggesting Sr2NiRuO4 as an unusual high-TC layered FM insulator. This work highlights the potential of charge-spin-orbital degrees of freedom for stabilizing strong FM coupling in layered oxides.