Caoshui Xiong

Fourier transform infrared characterization of nanometre

Fourier transform infrared transmission and reflectance spectra of nanometer with particle sizes ranging from 4 to 80 nm have been recorded at room temperature. The results show that even in very small sizes (4-8 nm), the grains retain the main features of rutile structure. Two surface modes at 640 and 520 without specific symmetries have been identified. The peak at 550 manifests the lattice imperfections in bigger nanometre samples. The present results indicate that the FT-IR technique is more sensitive than Raman scattering in the characterization of the transformation from nano-grains to polycrystalline.

Infrared spectra of nanometre granular zirconia

High-quality Fourier-transform infrared reflectance spectra of nanometre grains with particle sizes ranging from 5 nm to 120 nm have been recorded at room temperature. The results show that, even for very small grain sizes (5-10 nm), the samples retain the main features of monoclinic symmetry, although the lowering of the crystal symmetry has led to the broadening of the infrared bands. Two surface phonons have been identified. The processes of strain removal above the annealing temperature have been revealed by the appearance of two doublets at around and ; at the same time the particle sizes increase rapidly. As the particle size decreases, the doubly degenerate infrared-active modes, such as at , redshift while the non-degenerate modes, such as at , blueshift. This phenomenon is tentatively explained in terms of the internal-external classification of the lattice vibrations.

Fe doping effects on the magnetic and transport properties in La0.67Sr0.33Mn1−xFexO3

Abstract The X-ray diffraction patterns, susceptibility, electron magnetic resonance and resistivity in La 0.67 Sr 0.33 Mn 1− x Fe x O 3 have been studied systematically. With increasing Fe concentration, T c and the shift of resonance field H r decrease, the resistivity (two resistivity transition peaks were observed in x =0.07, 0.10) increases, but the lattice constants remain almost unchanged. When x =0.23, the spin glass-like state is observed and the system behaves insulator-like. The above results strongly suggest that the dopant Fe ions weaken the double exchange interaction.

A study on transport and electron paramagnetic resonance in

Temperature dependencies of the transport, the electron paramagnetic resonance (EPR) and the lattice parameters of polycrystalline Pb were studied. The anomalous behaviour of the lattice constant near the Curie temperature reveals that there is a strong lattice-magnetism coupling in this system. The variations of the resistivity and thermoelectric power above can be regarded as being due to the existence of small polarons arising from Jahn-Teller lattice distortion. It was found that all these phenomena coincide with the EPR results which exhibit completely different behaviours in delocalized and localized states. It is thus suggested that the colossal magnetoresistance effect originates from the actions both of the double exchange interaction and of the small polarons.

The preparation and demonstration of epitaxial La0.67Sr0.33MnO3−δ films/((110) orientation)

Abstract The X-ray diffraction patterns and pole figures of the La 0.67 Sr 0.33 MnO 3− δ films, which were fabricated on (110) LaAlO 3 single-crystal substrates using the direct current magnetron sputtering technique were studied systematically. It is concluded that all films are high-quality epitaxial films and there is a perfect matching relationship between the films and the substrates. The effect of the different orientations ((110) and (100)) on the resistivity and metal–insulator transition temperature is briefly discussed.

Investigation of Raman spectrum for nano-SnO2

The dependence of the microstructural change and lattice space symmetry of nano-SnO2 on the annealing temperature has been studied systematically using Raman spectroscopy and X-ray diffraction. Comparing the results of nano-SnO2 with the results of amorphous film and single crystal of SnO2, it is found that the new Raman peaks N1 and N2 are in accordance with Matossi’s force constant model completely. When the annealing temperature is near 673K, the local lattice disorders and the density of vacant lattice decrease rapidly in the nano-SnO2 grains. The lattice distortion and the new Raman peaks disappear almost at the same time. The possible mechanisms of the microstructural change and the new Raman peaks N1 and N2 are discussed.

The X-ray diffraction study of epitaxial La0.67Sr0.33MnO3 single crystal thin film

THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a large CMR effect and a high critical temperature T c shown in...

Interface interaction and inter-osmosis effect of Fe x (SiO2)1-x nanocomposite materials on magnetic properties

Fex(SiO2)1-x nanocomposites prepared by using mechanical alloying method were reported. The microstructure character and magnetic properties of Fex(SiO2)1-x nanocomposite samples with different Fe content and different ball milling time were studied by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, and Faraday magnetic balance in a wide temperature range. The results indicate that the rnicrostructure and magnetic properties are closely related to ball milling time and Fe content. When Fe content is less than 20 wt%, the sample after 80-h ball milling has very complex microstructure. Small α-Fe grains and Fe cluster are implanted in SiO2 matrix. And there are not only isolated α-Fe granular and Fe cluster, but also nanometer scaled sandwich network-like structure. Fex(SiO2)1-x nanocomposite samples display a rich variety of physical and chemical properties as a result of their unique nanostructure, strong interface interaction and inter-osmosis effect in Fe-SiO2 boundaries, and the grain size effect.

Tunneling planer Hall effect in Ni81Fe19/ Al2O3/NixFe1− x junction

Tunneling planer Hall (TPH) effect in Ni81 Fe19/Al2O3/NixFe1−x trilayer junction is different from general planer Hall effect in single-layer film or two-layer junction. This effect concerns the spin-polarized transport, so that the TPH voltage depends on the angle between magnetic vectors of two ferromagnetic layers. The TPH effect is reported to be influenced by composition and magnetic properties of FM layers and the thickness of the insulating layer.

Preparation, structure, magnetic properties and special magnetoresistance effect of Lao.67Sr0.33Mn03+δ/Pr0.7Cao.3 Mn03+δ/Lao.67Sro.33Mn03+δ trilayered thin films

The La0,67Sr0.33Mn03 +δ/Pr0.7Cao.3Mn03+δ/La0.67Sr0.33Mn03+δ(LPL) trilayered films on (100)LaA-1O3 substrates are prepared by using direct current (DC) magnetron sputtering method. The results obtained by means of X-ray powder diffractometer show that all films are the high quality epitaxial films. The results gained by SQUID magnetometer indicate that there is a magnetic coupling in the LPL trilayered films. The resistivities of LSMO, PC-MO and LPL films are measured using standard four-probe method and analyzed logp-1/T curve. From the results it is concluded that the middle-layered PCMO which is ferromagnetic may play a role of intra-magnetic field, which weakens the paramagnetism of LSMO film, lowerspmax and enlargesTp which is the transition temperature from metal to insulator, just as the applied magnetic field does. And the middle-layered PCMO may induce the change of the density of states in the LSMO’s gap. The two reasons above make the resistivity andTp of the samples in zero field change with the thickness of PCMO layers.