Magnetic and Magnetocaloric Dynamics in A2BFeO6 Double Perovskites: Impact of A and B Site Variations Analyzed Through Monte Carlo simulation and Ab initio calculations

Abstract

We investigate the magnetic and magnetocaloric properties of the double perovskites and using a combination of Monte Carlo simulations and Density Functional Theory (DFT). The exchange couplings were calculated using DFT. exhibits antiferromagnetic ordering with two transitions at 50 and 150 K, driven by strong antiferromagnetic exchange interactions between Fe³⁺ and Os⁵⁺ ions. In contrast, shows ferrimagnetic behavior with a single transition around 75 K, attributed to ferromagnetic coupling between Co2⁺ and Fe³⁺ ions. For the rare-earth-containing compounds, demonstrates complex magnetic ordering with transitions at approximately 20 K and 140 K, influenced by the strong spin-orbit coupling of Dy³⁺ ions. Similarly, exhibits two transitions at around 60 K and 170 K, reflecting a mix of ferromagnetic and antiferromagnetic interactions involving Dy³⁺, Co2⁺, and Fe³⁺ ions. shows a peak magnetic entropy change of 0.22 J/kg.K under a 5 T field at 50 K, while exhibits a broader peak at 75 K with of 1.5 J/kg.·K. presents significant peaks at 20 K and 140 K, reaching 1.9 J/kg·K under a 5 T field. displays the highest of 4.0 J/kg.·K at 60 K.