Above-room-temperature strain-stable half-metallic phase owing to a high thermoelectric response in CaCu3Cr2Re2O12

Abstract

We present the electronic, magnetic, and thermoelectric properties of the CaCu₃Cr₂Re₂O₁₂ quadruple double perovskite oxide (QDPO) using ab initio calculations. Strong antiferromagnetic interactions between Cu²⁺↑Cr³⁺↑Re⁵⁺↓ result in a ferrimagnetic (FiM) ground state. A half-metallic (HM) state is evident with a finite energy gap (E_g) of 1.62 eV in the spin-majority channel (N^↑), which is large enough to ensure a long mean free path for spin and prevent spin-flipping with a colossal spin-filtering ability. Due to a significant E_g in N^↑, the system displays a high figure of merit (0.76) at 300 K. The calculated spin moments of +0.48/+2.55/−0.92 μ_B and spin-magnetization densities on the Cu/Cr/Re further verify the FiM state. The magnetic phase transition yields a Curie temperature (T_C) of 340 K, which is below the experimental value (360 K). Because thermal energy near T_C disrupts the magnetic ordering, magnetization is consequently reduced, which is also reflected in the susceptibility curve. Additionally, the FiM state of the structure was confirmed under modulated applied magnetic fields. Finally, the HM FiM state is also verified under a moderate biaxial ([110]) strain of ±5%. Hence, this work provides deep insights into this QDPO, highlighting its stable HM FiM behavior, above-room-temperature T_C and high thermoelectric response, which promises potential applications in spintronics.