Báo cáo hóa học: Electronic and magnetic properties of SnO2/CrO2 thin superlattices

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Electronic and magnetic properties of SnO2/CrO2 thin superlattices
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Báo cáo hóa học: " Electronic and magnetic properties of SnO2/CrO2 thin superlattices"Borges et al. Nanoscale Research Letters 2011, 6:146http://www.nanoscalereslett.com/content/6/1/146 NANO REVIEW Open AccessElectronic and magnetic properties of SnO2/CrO2thin superlatticesPablo D Borges1*, Luísa MR Scolfaro2, Horácio W Leite Alves3, Eronides F da Silva Jr4, Lucy VC Assali1 Abstract In this article, using first-principles electronic structure calculations within the spin density functional theory, alternated magnetic and non-magnetic layers of rutile-CrO2 and rutile-SnO2 respectively, in a (CrO2)n(SnO2)n superlattice (SL) configuration, with n being the number of monolayers which are considered equal to 1, 2, ..., 10 are studied. A half-metallic behavior is observed for the (CrO2)n(SnO2)n SLs for all values of n. The ground state is found to be FM with a magnetic moment of 2 μB per chromium atom, and this result does not depend on the number of monolayers n. As the FM rutile-CrO2 is unstable at ambient temperature, and known to be stabilized when on top of SnO2, the authors suggest that (CrO2)n(SnO2)n SLs may be applied to spintronic technologies since they provide efficient spin-polarized carriers.Introduction Theoretical methodA variety of heterostructures have been studied for spin- All the calculations were based on the spin density func-tronics applications, and they have proved to have a great tional theory. The Projector-Augmented Wave methodpotential for high-performance spin-based electronics implemented in the Vienna Ab-initio Simulation Package[1]. A key requirement in developing most devices based (VASP-PAW) [5,6] was employed in this study, and foron spins is that the host material must be ferromagnetic the exchange-correlation potential, the generalized gradi-(FM) above 300 K. In addition, it is necessary to have effi- ent approximation and the Perdew, Burke, and Ernzerhofcient spin-polarized carriers. One approach to achieve (GGA-PBE) approach was used [7]. The valence electro-the spin injection is to create built-up superlattices (SLs) nic distribution for the PAWs representing the atoms were Sn– 4d10 5s2 5p2, Cr– 3d5 5s1, and O-2s2 2p4. Scalarof alternating magnetic and non-magnetic materials. Oneattempt has already been made by Zaoui et al. [2], relativistic effects were included. For simulation of thethrough ab initio electronic structure calculations for the one monolayer (CrO2)1 (SnO2 )1 SL, a supercell with 12one monolayer (ZnO)1(CuO)1 SL, with the aim of obtain- atoms (2Sn, 2Cr, and 8O) in the rutile structure as showning a half-metallic behavior material, since they are 100% in Figure 1a was used. For this case, a 4 × 4 × 3 mesh ofspin polarized at the Fermi level and therefore appear Monkhorst-Pack k-points was used for integration in theideal for a well-defined carrier spin injection. SL BZ. All the calculations were done with a 490 eV In this study, the magnetic and electronic properties energy cutoff in the plane-wave expansions.of (CrO 2 ) n(SnO 2 ) n SLs with n = 1, 2, ..., 10 being the Results and discussionnumber of monolayers are investigated. These systemsare good candidates to obtain a half-metallic behavior For the (CrO2)1(SnO2)1 SL, the calculation was startedmaterial since bulk rutile-CrO2 has shown experimen- with the experimental lattice parameters of the tin diox-tally this behavior [3] and recently magnetic tunnel ide, a = 4.737 Å, c/a = 0.673, and u = 0.307 [8-10]. Thejunctions based on CrO 2 /SnO 2 epitaxial layers have system was relaxed until the residual forces on the ionsbeen obtained [4]. were less than 10 meV/Å. Good agreement between the calculated and the available experimental values for the l ...