Atomic and electronic structure of CNT/LSMO-based nanocomposites: a DFT study

Complex half-metallic manganites La 1-xSr xMnO 3 (LSMO) are promising materials for spintronic and spicaloritronic applications due to 100 % of spin polarization. Using spin-polarized currents through LSMO-graphene interfaces a number of LSMO-based high-efficiency organic LED and spin-valve nanodevices have been developed. Large magnetoresistance effects bonded with large output signals were detected in a nanodevice. The device of multiwall carbon nanotube that spans a gap between spin-polarized half-metallic La 0.7Sr 0.3MnO 3 electrodes demonstrated long spin lifetime and high Fermi velocity in the nanotube, the high spin polarization of the manganite electrodes and the resistance of the interfacial barrier for spin injection. The experimental results were supported by density functional theory calculations. Interfaces of La 0,67Sr 0,33MnO 3 with armchair and zigzag carbon nanotubes (CNT) were studied by means of quantum chemistry within density functional theory. All calculations were performed using generalized gradient approximation with Hubbard correction (GGA+U) and Grimme correction of dispersion interaction. Different configurations of composite compartments mutual arrangement were considered. The analysis of partial densities of states (PDOS) reveals the influence of substrate on nanotube’s electronic structure. The possibility of nanotubes’ spin polarization and utilization of such nanocomposites in spintronics is also discussed. It was found that interaction between carbon nanotubes and LSMO slab lead to major deformation of the tube due to the difference in structural parameters of composite compartments. Zigzag (9,0) nanotube is contracted by 9% while armchair (5,5) nanotube is stretched by 5 %. Although this deformation results in significant change in nanotube’s electronic structure, there is no visible difference between spin-up and spin-down PDOSes of the tubes. Composites are then almost totally spin-polarized due to the presence of LSMO.