Zheng-Bin Gu

Structure, optical, and magnetic properties of sputtered manganese and nitrogen-codoped ZnO films

To realize the hole-mediated ferromagnetism, manganese and nitrogen-codoped ZnO (Zn1−xMnxO:N) films were prepared on sapphire (0001) by reactive radio-frequency (rf) magnetron sputtering from Zn0.97Mn0.03O ceramic targets using N2 gas. X-ray photon spectra reveal that the doped Mn ions are mainly in divalent states and the coexistence of O–Zn and N–Zn bonds in the films. According to the absorption spectra, the band gap of Zn0.97Mn0.03O:N films is about 3.15eV, which is slightly lower than that of ZnO films (3.20eV). Compared with Zn0.97Mn0.03O films, ferromagnetic behavior of Zn0.97Mn0.03O:N films were significantly changed with a coercivity of about 70Oe, a saturation magnetization of 0.92μB∕Mn2+ and a remanance over 0.15μB∕Mn2+ at 300K, while at 10K, they increased to be about 110Oe, 1.05μB∕Mn2+ and 0.23μB∕Mn2+, respectively. However, rapid thermal annealing treatment in pure oxygen results in a significant decrease on the magnetic properties of the films.

Magnetic and transport properties of (Mn, Co)-codoped ZnO films prepared by radio-frequency magnetron cosputtering

(Mn, Co)-codoped ZnO films have been synthesized on c-sapphire (0001) by a radio-frequency magnetron sputtering system in which two targets were sputtered together. X-ray-diffraction measurements indicate that the films are highly c-axis oriented. X-ray photon spectra show that the doped Mn and Co ions in (Mn, Co) ZnO films are both in the divalent states. The films show ferromagnetic behavior with a coercivity of about 90 Oe and a saturation moment of 0.11μB∕(0.3Mn2++0.7Co2+) at 300 K. In the lower temperatures between 5 and 20 K, a relatively large positive magnetoresistance over 10% was observed for (Mn0.03,Co0.07)Zn0.90O film. The number of carrier concentration is experimentally established to be 1.5613×1018cm−3 and the mobility to be 2.815cm2V−1s−1 for (Mn0.03,Co0.07)Zn0.90O film by Hall measurements at 300 K. The origins of the room-temperature magnetism and the large positive magnetoresistance are also discussed.(Mn, Co)-codoped ZnO films have been synthesized on c-sapphire (0001) by a radio-frequency magnetron sputtering system in which two targets were sputtered together. X-ray-diffraction measurements indicate that the films are highly c-axis oriented. X-ray photon spectra show that the doped Mn and Co ions in (Mn, Co) ZnO films are both in the divalent states. The films show ferromagnetic behavior with a coercivity of about 90 Oe and a saturation moment of 0.11μB∕(0.3Mn2++0.7Co2+) at 300 K. In the lower temperatures between 5 and 20 K, a relatively large positive magnetoresistance over 10% was observed for (Mn0.03,Co0.07)Zn0.90O film. The number of carrier concentration is experimentally established to be 1.5613×1018cm−3 and the mobility to be 2.815cm2V−1s−1 for (Mn0.03,Co0.07)Zn0.90O film by Hall measurements at 300 K. The origins of the room-temperature magnetism and the large positive magnetoresistance are also discussed.

Intrinsically modified thermoelectric performance of alkaline-earth isovalently substituted [Bi2AE2O4][CoO2]y single crystals

Alkaline-earth elements isovalently substituted into a [Bi2AE2O4][CoO2]y (AE2 = Ca2, Sr2, and CaSr) single crystal with a layered structure were grown by the optical floating zone method. Structural characterization by X-ray diffraction and electron microscopy showed that the layers were oriented perpendicular to the c-axis, as well as the growth of direction was parallel to the ab-plane. The thermoelectric properties, including the Seebeck effect, electrical conductivity and thermal conductivity were investigated. The results of the thermoelectric measurements showed that the full substitution of Ca for Sr in [Bi2Sr2−xCaxO4][CoO2]y has the best overall thermoelectric performance. Compared with the other two cases studied, the full Ca substituted crystal [Bi2Ca2O4][CoO2]y exhibits both reduced resistivity and thermal conductivity, but not a reduced Seebeck coefficient. The enhanced thermoelectric property in [Bi2Ca2O4][CoO2]y is mainly due to lower structural symmetry, which is confirmed by electron micro...

Giant magnetoresistance in transition-metal-doped ZnO films

Magnetic and transport properties were investigated in Zn0.94Mn0.03Co0.03O thin films prepared by dual radio frequency magnetron sputtering technique. A negative magnetoresistance (MR=[ρ(H)−ρ(0)]∕ρ(0)) of −95% at 2K and a positive MR of 48% at 10K were established in the films. The anomalous magnetic and magnetic-related transport properties in transition-metal-doped ZnO films are discussed in terms of magnetic polarons.

Metal–insulator transition in SrIrO3 with strong spin–orbit interaction

The thickness-dependent metal-insulator transition is observed in meta-stable orthorhombic SrIrO3 thin films synthesized by pulsed laser deposition. SrIrO3 films with thicknesses less than 3 nm demonstrate insulating behaviour, whereas those thicker than 4 nm exhibit metallic conductivity at high temperature, and insulating-like behaviour at low temperature. Weak/Anderson localization is mainly responsible for the observed thickness-dependent metal-insulator transition in SrIrO3 films. Temperature-dependent resistance fitting shows that electrical-conductivity carriers are mainly scattered by the electron-boson interaction rather than the electron-electron interaction. Analysis of the magneto-conductance proves that the spin-orbit interaction plays a crucial role in the magneto-conductance property of SrIrO3.

Tunable semimetallic state in compressive-strained SrIr O 3 films revealed by transport behavior

Orthorhombic

Sensitively Temperature-Dependent Spin–Orbit Coupling in SrIrO3 Thin Films

\mathrm{SrIr}{\mathrm{O}}_{3}

Ferromagnetism in Mn and Sb co-doped ZnO films

is a typical spin-orbit-coupled correlated metal that shows diversified physical properties under external stimuli. Here the nonlinear Hall effect and weakly temperature-dependent resistance are observed in a

Giant positive magnetoresistance in half-metallic double-perovskite Sr2CrWO6 thin films

\mathrm{SrIr}{\mathrm{O}}_{3}

Strong correlation of the growth mode and electrical properties of BiCuSeO single crystals with growth temperature

film epitaxially grown on a