Search results

1

Investigations on the Anisotropic g Factors of the Ni^{3+} Site in La_2Ni_{0.5}Li_{0.5}O_4

100%

Kuang M., Wu S., Zhang Z., Song B.

Acta Physica Polonica A

|

2013

|

vol. 123

|

issue 4

734-736

EN

The anisotropic g factors g_{∥} and g_{⊥} of La_2Ni_{0.5}Li_{0.5}O_4 are theoretically investigated using the perturbation formulae of the g factors for a low spin (S=1/2) 3d^7 ion in tetragonally elongated octahedra. The studied Ni^{3+} (3d^7) center arises from the original Ni^{2+} capturing one hole by Li^{+} doping. The positive anisotropy Δ g (= g_{⊥}-g_{∥}) can be ascribed to the lowest ^2 A_{1g} state due to the obvious (about 0.14 Å) tetragonal elongation of the oxygen octahedron around the Ni^{3+} site via the Jahn-Teller effect, and the effective magnetic moment is also interpreted in a uniform way. The calculated results show good agreement with the experimental data, and the imperfection of the previous studies based on various adjusted tetragonal energy splittings without correlating to the local structure of the magnetic center is thus overcome in this work.

2

Mechanical Properties of Magnesium Alloys Produced by the Heated Mold Continuous Casting Process

100%

Okayasu M., Wu S., Tanimoto T., Takeuchi S.

|

3

Theoretical Studies of the Spin Hamiltonian Parameters and Local Structures for the Two Tetragonal Cu^{2+} Centers in Ca(OH)_2

100%

Zhang H., Wu S., Zhang Z.

|

EN

The spin Hamiltonian parameters (g factors g_{∥ }, g_{⊥} and the hyperfine structure constants A_{∥ }, A_{⊥}) and the local structures for the two tetragonal Cu^{2+} centers I and II in Ca(OH)_2 are theoretically studied from the perturbation formulae of these parameters for a 3d^9 ion under tetragonally elongated octahedra. The [Cu(OH)_6]^{4-} clusters on the substitutional Ca^{2+} site are found to suffer the relative elongations by about 0.083 Å and 0.065 Å for centers I and II, respectively, along the C_4 axis due to the Jahn-Teller effect. The above tetragonal elongations may entirely depress the original trigonal distortion of the host Ca^{2+} site in Ca(OH)_2. The calculated spin Hamiltonian parameters based on the above Jahn-Teller elongations show good agreement with the experimental results. The EPR spectra and the local structures for the two centers are compared with one another.

4

Advanced Characterization of Material Properties on the Nanometer Scale Using Atomic Force Microscopy

88%

Fenner M., Wu S., Yu J., Huber H., Kienberger F.

Acta Physica Polonica A

|

2012

|

vol. 121

|

issue 2

416-419

EN

We report recent advances in material characterization on the nanometer scale using scanning microwave microscopy. This combines atomic force microscopy and a vector network analyzer using microwave tip sample interaction to characterize dielectric and electronic material properties on the nanometer scale. We present the methods for calibration as well as applications. Scanning microwave microscopy features calibrated measurements of: (1) capacitance with attofarad sensitivity. For calibration a well characterized array of capacitors (0.1 fF to 10 fF) is used. The method is applied to determine the dielectric properties of thin organic films, (2) Semiconductor dopant density. Calibration is performed by imaging the cross-section of a standard sample with differently doped layers (dopant stair case) from 10^{16} atoms/cm^3 to 10^{20} atoms/cm^3.

5

Investigations on the EPR Parameters of KMgF_3:Cr^{+}

88%

Kuang M., Wu S., Hu X., Li G., Zu H.

|

vol. 125

|

issue 5

1224-1228

EN

The electron paramagnetic resonance parameters (i.e., g factor, hyperfine structure constant and superhyperfine parameters) of KMgF_3:Cr^{+} are theoretically investigated from the perturbation formulae of these parameters for an octahedral 3 d^5 cluster. As for the calculations of g factor and hyperfine structure constant, both the contributions from the crystal-field and charge transfer mechanisms are included based on the cluster approach. The metal to ligand charge transfer contribution to the g-shift Δg ( ≈ g-2.0023) is the same (negative) in sign and much larger in magnitude as compared to the crystal-field one. The conventional argument that the charge transfer contributions to zero-field splittings are negligible for 3 d^5 ions in fluorides is no longer suitable for Δg analysis of KMgF_3:Cr^{+} due to the dominant second-order charge transfer perturbation term. The charge transfer contribution to hyperfine structure constant exhibits the same sign and about 4% of the crystal-field one. The unpaired spin densities of the fluorine 2s, 2pσ and 2pπ orbitals are quantitatively acquired from the relationships with the relevant molecular orbital coefficients using the uniform model. The present treatments are superior to the previous calculations of directly fitting the experimental superhyperfine parameters.

6

Raman Spectroscopy of LiFePO_4 and Li_3V_2(PO_4)_3 Prepared as Cathode Materials

76%

Ziółkowska D., Korona K., Kamińska M., Grzanka E., Andrzejczuk M., Wu S., Chen M.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 5

973-975

EN

Structure of samples of lithium iron vanadium phosphates of different compositions were investigated by X-rays, electron microscopy and Raman spectroscopy. The investigated salts were mainly of olivine-like and NASICON-like structures. The X-ray diffraction and the Raman scattering show different crystalline structures, which is probably caused by difference between cores of the crystallites (probed by X-rays) and their shells (probed by the Raman scattering). Most of the Raman spectra were identified with previously published data, however in the samples with high vanadium concentration we have observed new, not reported earlier modes at 835 cm^{-1} and 877 cm^{-1}, that we identified as oscillations related to V_2O_7^{4-} or VO_4^{3-} anions.

7

The Design and the First Test Results of a Fast LTD Stage

64%

Chen L., Zhou L., Zou W., Ren J., Li Y., Wu S., Xie W., Feng S., Deng J.

Acta Physica Polonica A

|

2009

|

vol. 115

|

issue 6

1186-1188

EN

Linear transformer driver stages are designed to be used as a primary energy storage in high power pulsed generators. In this report, the design and test results of the linear transformer driver stage prototype that delivers ≈100 kA fast pulse with 133 ns FWHM into a ≈0.87 Ω resistive load are described. This stage consists of 20 (100 kV, 20 nF) storage capacitors that are arranged in 10 identical bricks located evenly around the axis of the stage. Each brick contains two capacitors, a multi-gap switch, and the output connector that transfers the energy to the resistive load. The outer diameter of the stage is ≈1.5 m, at a length of ≈20 cm. The stage is developed to demonstrate the possibility of the fast linear transformer driver technology to create high power pulsed generators.

8

Ultrafast Phenomena in Freestanding LT-GaAs Devices

52%

Marso M., Mikulics M., Adam R., Wu S., Zheng X., Camara I., Siebe F., Förster A., Güsten R., Kordoš P., Sobolewski R.

Acta Physica Polonica A

|

2005

|

vol. 107

|

issue 1

109-117

EN

We report on the fabrication and high-frequency performance of our photodetectors and photomixers based on freestanding low-temperature-grown GaAs. The MBE-grown low-temperature GaAs layers are lifted from the native GaAs substrate and transferred on top of variety of host substrates. The freestanding devices exhibit breakdown electrical fields above 200 kV/cm and dark currents below 3×10^{-7} A at 100 V bias. Device photoresponse shows 0.55 ps wide electrical transients with voltage amplitudes up to 1.3 V, measured using an electro-optical sampling technique with 100 fs wide laser pulses. Photomixing experiments at 460 GHz yield a 9 times higher output power for the freestanding device on Si/SiO_2 host substrate compared to the native substrate.

Refine search results

Investigations on the Anisotropic g Factors of the Ni^{3+} Site in La_2Ni_{0.5}Li_{0.5}O_4

Mechanical Properties of Magnesium Alloys Produced by the Heated Mold Continuous Casting Process

Theoretical Studies of the Spin Hamiltonian Parameters and Local Structures for the Two Tetragonal Cu^{2+} Centers in Ca(OH)_2

Advanced Characterization of Material Properties on the Nanometer Scale Using Atomic Force Microscopy

Investigations on the EPR Parameters of KMgF_3:Cr^{+}

Raman Spectroscopy of LiFePO_4 and Li_3V_2(PO_4)_3 Prepared as Cathode Materials

The Design and the First Test Results of a Fast LTD Stage

Ultrafast Phenomena in Freestanding LT-GaAs Devices