# Tuning Interfacial Ferromagnetism in LaNiO$_3$/CaMnO$_3$ Superlattices by Stabilizing Non-Equilibrium Crystal Symmetry

## TL;DR

This study demonstrates how non-equilibrium crystal symmetries in LaNiO$_3$/CaMnO$_3$ superlattices can be engineered to control interfacial ferromagnetism, with modulation factors up to three based on layer thickness and ratio.

## Contribution

It reveals the role of non-equilibrium crystal symmetries in tuning ferromagnetism in perovskite superlattices, a novel approach for magnetic property control.

## Key findings

- Interfacial ferromagnetism varies threefold with layer adjustments.
- Non-equilibrium symmetries influence exchange interactions and bond angles.
- Layer thickness and ratio are key parameters for magnetic tuning.

## Abstract

Perovskite oxide heterostructures offer an important path forward for stabilizing and controlling low-dimensional magnetism. One of the guiding design principles for these materials systems is octahedral connectivity. In superlattices composed of perovskites with different crystal symmetries, variation of the relative ratio of the constituent layers as well as the individual layer thicknesses gives rise to non-equilibrium crystal symmetries that, in turn, lead to unprecedented control of interfacial ferromagnetism. We have found that in superlattices of CaMnO$_3$ (CMO) and LaNiO$_3$ (LNO), interfacial ferromagnetism can be modulated by a factor of three depending on LNO and CMO layer thicknesses as well as their relative ratio. Such an effect is only possible due to the non-equilibrium crystal symmetries at the interfaces and can be understood in terms of the anisotropy of the exchange interactions and modifications in the interfacial Ni-O-Mn and Mn-O-Mn bond angles and lengths with increasing LNO layer thickness. These results demonstrate the potential of engineering non-equilibrium crystal symmetries in designing ferromagnetism.