| The structure characteristics and electromagnetic properties of the A2BB’O6type double perovskite oxide has been made some exploration in the early1950s, but scattered just from the aspects of synthesis about the preparation conditions and lattice structure have got in the after decades because of the still very immature development of related applications. In1998Kobayashi and others found10%of the tunneling magnetoresistance effect in Sr2FeMoO6at room temperature, so double perovskite oxide as a wider class of the object of study immediately became one of the most likely to use in room temperature magnetoresistance materials.From a theoretical point of view, this kind of double perovskite oxide system has more rich transformation combination, and the theoretical workers have broad space for modeling, such as B and B’ions of different electronic configuration and ionic radius and the kinds of exchange interaction, so people can change these combinations to explore many different types of problems, for many electronic systems strongly associated interaction, electronic transport, and the exploration of specific properties such as spin arrangement provides has significant academic value of the object of study. On this basis, the double perovskite oxide material aspects, such as electric and magnetic properties of the extremely valuable. The orderly double perovskite Sr2FeReO6is one of the widely research material. Research proves that it has half-metal properties, and the experimental results showed that the Curie temperature of a polycrystalline sample is as high as401k, there are obvious low field TMR effect. In order to get more detailed understanding of the double perovskite electronic structure and magnetic exchange, people usually in double perovskite/magnetic metal ion (such as A, B and B’) the location of the doping or using electronic to do in-depth research, the double perovskite Sr2FeReO6doping has become a hot research in recent years, such as Ga, Ca, Cr, Nb and Ta on Sr2FeReO6doping.Recently Maria Retuerto et al. adopt the method of neutron powder diffraction with the structure of the two same Sr2CoReO6crystal structure and magnetic structure of experimental study show that at room temperature, Sr2CoReO6perovskite crystal structure of quadrangular, space group of I2/m, almost completely ordered arrangement of the tilted CoO6and contains ReO6octahedron. With lower temperature, its experience a phase transition into monoclinic symmetry, space group of P21/n. In terms of magnetic structure, low temperatures, Sr2CoReO6for ferromagnetic, Co2+ion in the S=3/2high spin state, Neil temperature is only2-60k. However, experimental study and not to Sr2CoReO6electronic structure is discussed, the current for W doped double perovskite oxide theoretical calculation, the report has yet to see this paper based on first principles under the framework of density functional theory calculations, the use of the under the generalized gradient approximation projection compose and wave potential, double perovskite oxide was studied in detail Sr2CoReO6and Sr2FeRe1-xWxO6(x=0.00,0.25,0.50,0.75,1.00) of magnetic and electronic structure, in order to from the angle of theoretical calculation of double perovskite Sr2CoReO6and Sr2FeRe1-xWxO6(x=0.00,0.25,0.50,0.75,1.00) properties were studied. Received the following valuable research results:1) The magnetic moments of Co2+and Re5+are2.425and-0.488μB respectively and thus antiferromagnetic coupling via oxygen between them.2) Both occupied and unoccupied s and three p states of Co2+ion are located far away from the Fermi level, while all up-spin states and most down-spin states are completely filled for the s and three p states of Re5+ion.3) The presence of the cubic symmetry of the octahedral coordination of the oxygen atoms around Co/Re site results in a splitting of the five-fold degenerate d states of a free Co/Re atom into triply degenerate t2g (dxy, dyz and dzx) states with lower energy and doubly degenerate eg (dz2and dx2-y2) states with higher energy for either up-spin or down-spin.4) There are no direct interactions between two nearest Co-Co or Re-Re pairs, whereas along each Co-O-Re-O-Co or Re-O-Co-O-Re chains, the hybridizations between Co3d and4s, O2s and2p, as well as Re5p,5d and6s orbitals are fairly significant.5) With increasing W content x, the cell volume, the band gap in up-spin channel and the magnetic moment of the W/Re atoms have an increasing tend.6) No obvious changes have been observed for the magnetic moment of the Fe atom.7) More importantly, the half-metallic (HM) nature is still maintained for various W contents, implying the potential applications of the W doped double perovskite Sr2FeRe1-xWxO6in spintronic devices. |
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