First-principle Studies On The Electronic Structure And Magnetic Properties Of Double Perovskite Materials

In the past fifty years, double perovskites have been caused people's attention due to their excellent magnetic and transport properties. The interest in double perovskite has been renewed since the report of room temperature magnetoresistance (TMR) and half-metallic conduction properties of Sr₂ FeMoO₆. In 1990s, it is useful in magnetic memory, magnetic sensor, thermal hysteresis and charge order transformation. In such a case, we simulate and calculate its electron structure, magnetic and half-metallic properties using the First Principles Calculations method. In resent years, the computer technology has been got rapid growth and it is possible to complete this task.The present tasks are performed within generalized gradient approximation (GGA) to the density functional theory (DFT), using the full-potential linearized augmented plane waves (FP-LAPW) method. We calculated its electronic structure, magnetic and half-metallic properties of Ca₂ CrSbO₆. It is a novel double perovskite material which was synthesized in 2006. According the experimental, it is the first ferromagnetic material containing the nonmagnetic in the B '' position.The results show that Ca₂ CrSbO₆ has a stable ferromagnetic ground state, its magnetic moment is 2.99μ_B in one unit cell, the element of Cr contribute the most component; there exist a strong hybridization between the 2p states of O and the 3d states of Cr; By analyzed the charge density and the bond angle, we proposed that the Sb 5p states within O 2p states satisfy the overlap of Cr 3d orbitals, promoting the observed ferromagnetic interactions. Our results show that it is a half-metallic material. Besides, we used this method studied the double perovskiteSr₂ MSbO₆(M=Mn,Tc,Re), its optic, magnetic and electronic properties were calculated. We found that the magnetic properties is mostly coming from the contribution of element in the B' position, and the magnetic moment is decreased as the increment of the radius and ordinal number of this element. We studied the material's real and imaginary part and its static dielectric function were calculated, it was 8.1, 4.52, 3.75 respectively.