# Unveiling Insulating Ferro and Ferrimagnetism in Double-Double Perovskite Oxides

## TL;DR

This study predicts and analyzes insulating ferro- and ferrimagnetic double-double perovskite oxides, revealing their potential for spintronic and optical applications through symmetry analysis, first-principles calculations, and Monte Carlo simulations.

## Contribution

It introduces new insulating ferro- and ferrimagnetic perovskite materials with detailed mechanisms and stability analysis, advancing the understanding of magnetic properties in these compounds.

## Key findings

- Predicted LaA'MnNiO6 compounds as promising for spintronics and optics.
- Identified magnetic transition temperatures up to 242 K.
- Explained mechanisms of band gap opening and magnetic exchange.

## Abstract

The emergence of ferro- and ferrimagnetic behavior in insulating materials is uncommon, largely due to Hund's rules. Utilizing symmetry analysis, first-principles methods, and classical Monte Carlo simulations, \textcolor{black}{we report technologically important insulating ferro and ferrimagnetic double-double perovskite oxides. Our study predicts LaA$^{\prime}$MnNiO$_6$ (A$^{\prime}$ = V, Cr, Mn, Co, and Ni) as promising candidates for spintronic and optical applications exhibiting band gaps between 1.3 eV and 1.9 eV. We explain the mechanisms driving band gap openings and magnetic exchange interactions in these ferro and ferrimagnetic compounds. Monte Carlo simulations, together with state-of-the-art orbital-decomposed exchange parameter analysis, reveal intriguing variations in magnetic transition temperatures (up to 242 K) and the corresponding exchange mechanisms in all LaA$^{\prime}$MnNiO$_6$ compounds.} In addition, we assess the thermodynamic and dynamic stability of these compounds to comment on the feasibility of these systems.