# Role of polar compensation in interfacial ferromagnetism of LaNiO$_3$/CaMnO$_3$ superlattices

## TL;DR

This study reveals how polar compensation influences interfacial ferromagnetism in LaNiO3/CaMnO3 superlattices, showing different magnetic mechanisms depending on LaNiO3 layer thickness and emphasizing the importance of interface charge redistribution.

## Contribution

It demonstrates that polar compensation at the interface is crucial for understanding and controlling interfacial ferromagnetism in oxide heterostructures, with detailed analysis of magnetic interactions.

## Key findings

- Interfacial charge redistribution via polar compensation is key to ferromagnetism evolution.
- Ni-Mn superexchange dominates in insulating superlattices.
- Mn-Mn double-exchange becomes significant in metallic superlattices.

## Abstract

Polar compensation can play an important role in the determination of interfacial electronic and magnetic properties in oxide heterostructures. Using x-ray absorption spectroscopy, x-ray magnetic circular dichroism, bulk magnetometry, and transport measurements, we find that interfacial charge redistribution via polar compensation is essential for explaining the evolution of interfacial ferromagnetism in LaNiO$_3$/CaMnO$_3$ superlattices as a function of LaNiO$_3$ layer thickness. In insulating superlattices (4 unit cells or less of LaNiO$_3$), magnetism is dominated by Ni-Mn superexchange, while itinerant electron-based Mn-Mn double-exchange plays a role in thicker metallic superlattices. X-ray magnetic circular dichroism and resonant x-ray scattering show that Ni-Mn superexchange contributes to the magnetization even in metallic superlattices. This Ni-Mn superexchange interaction can be explained in terms of polar compensation at the LaNiO$_3$-CaMnO$_3$ interface. These results highlight the different mechanisms responsible for interfacial ferromagnetism and the importance of understanding compensation due to polar mismatch at oxide-based interfaces when engineering magnetic properties.