Emergence of insulating ferro- and ferrimagnetism with enhanced optical properties in double-double perovskite oxides

The emergence of ferro-and ferrimagnetic behavior in insulating materials is uncommon, largely due to Pauli’s exclusion principle, which typically favors antiferromagnetic spin alignment between neighboring species. Utilizing symmetry analysis, first-principles methods, and classical Monte Carlo simulations, we report technologically important insulating ferro-and ferrimagnetic double-double perovskite oxides. Our study identifies LaA ′ MnNiO6 (A ′ = V, Cr, Mn, Co, and Ni) as promising candidates exhibiting band gaps between 1.3 eV and 2.2 eV, calculated using the modified Becke-Johnson exchange-correlation potential. These compounds are particularly relevant for spintronic and optical applications. 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 ′ MnNiO6 compounds are discussed. Additionally, we assess the thermody-namic and dynamic stability of these compounds, confirming their feasibility for practical applications.