Shaojie Fang

Magnetism in Co-doped tris-8-hydroxyquinoline aluminum studied by first-principles calculations

The electronic and magnetic properties of Co-doped tris-8-hydroxyquinoline aluminum (Alq3) are studied by first-principles calculations. Our results indicate that the local magnetic moments in doped Alq3 originate from the localized d states of Co atom. Electron transfer takes place from Co atom to Alq3 molecule, which is mainly localized on the quinolate ligand, resulting in formation of bound magnetic polarons. The indirect ferromagnetic exchange interaction between two bound magnetic polarons antialigning with the same magnetic ion promotes the collective magnetism found in recent experiments.

Structure of Co-Doped Alq3 Thin Films Investigated by Grazing Incidence X-ray Absorption Fine Structure and Fourier Transform Infrared Spectroscopy

The structural properties of Co-doped tris(8-hydroxyquinoline)aluminum (Alq(3)) have been studied by grazing incidence X-ray absorption fine structure (GIXAFS) and Fourier transform infrared spectroscopy (FTIR). GIXAFS analysis suggests that there are multivalent Co-Alq(3) complexes and the doped Co atoms tend to locate at the attraction center with respect to N and O atoms and bond with them. The FTIR spectra indicate that the Co atoms interact with the meridional (mer) isomer of Alq(3) rather than forming inorganic compounds.

Magnetic properties of tris(8-hydroxyquinoline)iron: Experimental and theoretical investigation

The magnetic properties of tris(8-hydroxyquinoline)iron (Feq3) are investigated by experiments and first-principles density functional theory. In contrast to the diamagnetic behavior of Alq3, the Feq3 films deposited by vacuum thermal evaporating exhibit paramagnetic behaviors at 5 K. The calculated electronic structure of Feq3 molecule shows clear exchange splitting between the majority and minority spin channels. The total magnetic moment is about 1 μB, which mainly derives from the localized Fe 3d orbital. The paramagnetic behavior observed is ascribed to the small energy difference (1 meV) between ferromagnetic and antiferromagnetic coupling.

Annealing Effect on Transport and Magnetic Properties of La0.67Sr0.33MnO3 Thin Films Grown on Glass Substrates by RF Magnetron Sputtering

The manganite La 0.67 Sr 0.33 MnO 3 (LSMO) thin films were grown on glass substrates in a mixed argon and oxygen atmosphere by using RF magnetron sputtering. The structural characteristics, transport behaviors and magnetic properties of LSMO films were studied by annealing the films in air at 550 and 620°C. The out-of-plane lattice parameter a LSMO contracted after annealing and was close to that of bulk LSMO a bulk , indicating that the internal strain was fully relaxed. Nanocrystalline grains were observed in the annealed films. Enhanced saturation magnetization and metal-to-insulator transition temperature (T MI =268 K) were also obtained. Curie temperatures ( T c ) of the as-grown films was 340 K with the same as that of annealed at 550°C, but dropped to 315 K when the annealing temperature increased to 620°C, which can be attributed to the oxygen release during annealing in atmosphere.

The structure of Mn-doped tris(8-hydroxyquinoline)gallium by extended x-ray absorption fine structure spectroscopy and first principles calculations

Metal-Mqx (M = Al, Ga, Zn, Be, and Ca, x = 2 or 3) complexes play a key role in organic spintronics and organic optoelectronics. However, the accurate structure determination of these complexes has been a challenge for a long time. Here, we report the structure of Mn-Gaq3 investigated by using first-principle density functional theory (DFT) calculations and extended X-ray absorption fine structure (EXAFS) spectroscopy. First, the structures of Mn-Gaq3 were predicted by first-principle DFT calculations. Then, all reasonable structures achieved from the calculations were used to fit the EXAFS spectra. By this method, the structure of Mn-Gaq3 is well obtained. We believe this method is also applicable to other metal-Mqx films.