Magnetism of (LaCoO$_3$)$_n$+(LaTiO$_3$)$_n$ superlattices with $n=1,2$

TL;DR

This study uses first principles calculations to explore the magnetic and electronic properties of LaCoO$_3$-based superlattices, revealing high-spin Co$^{2+}$ states, antiferromagnetic order, and potential ferromagnetism upon hole doping.

Contribution

It provides new insights into the magnetic states and phase stability of LaCoO$_3$ superlattices with detailed analysis of electron transfer and orbital polarization.

Findings

Superlattices exhibit strong electron transfer from Ti to Co.

High-spin Co$^{2+}$ with antiferromagnetic order predicted.

Hole doping can stabilize ferromagnetic order on Co$^{2+}$.

Abstract

LaCoO$_3$ provides a poignant example of a transition metal oxide where the cobalt cations display multiple spin states and spin transitions and which continues to garner substantial attention. In this work, we describe first principles studies, based on DFT+$U$ theory, of superlattices containing LaCoO$_3$, specifically (LaCoO$_3$)$_n$+(LaTiO$_3$)$_n$ for $n=1,2$. The superlattices show strong electron transfer from Ti to Co resulting in Co$^{2+}$, significant structural distortions and a robust orbital polarization of Co$^{2+}$. We predict high-spin Co$^{2+}$ and a checkerboard or G-type antiferromagnetic (AFM) ground state. We provide a detailed analysis of the magnetic interactions and phases in the superlattices. We predict that ferromagnetic order on the Co${2+}$ can be stabilized by hole doping (e.g., replacing La by Sr) which is rather unusual for Co$^{2+}$ cations.