Cd₂FeReO₆: A High-T_C Double Perovskite Oxide with Remarkable Tunneling Magnetoresistance

In this study, we successfully synthesized the double perovskite oxide Cd₂FeReO₆ by using a high-temperature and high-pressure method. The crystal structure was confirmed to belong to the P2₁/n space group, exhibiting approximately 68% ordering of Fe³⁺ and Re⁵⁺ ions at the perovskite B-site with the remaining regions showing antisite disorder. The measured Curie temperature of Cd₂FeReO₆ was 460 K, slightly lower than expected but still significantly above room temperature. Remarkably, Cd₂FeReO₆ displayed a remarkable low-field butterfly type tunneling magnetoresistance of -23% (-37% between the lowest and the largest values) at 5 K and 90 kOe, the highest among the A₂FeReO₆ (A = Ca, Sr, Pb, Ba) family. First-principles calculations provided insight into the origin of this observed magnetoresistance behavior, revealing Cd₂FeReO₆'s half-metallic ferrimagnetic nature. This research extends our understanding of the double perovskite family and emphasizes its potential significance in the domains of spintronics and materials science. The exploration of differing magnetoresistance behaviors between Cd₂FeReO₆ and Ca₂FeReO₆, along with the influence of antisite disorder in Cd₂FeReO₆, opens intriguing avenues for further research.