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Full-Text Articles in Physical Sciences and Mathematics

Magnetic And Transport Properties Of Nimnal Thin Films, Andriy Vovk, Minghui Yu, Leszek Malkinski, Charles O'Connor, Zhenjun Wang, Eden Durant, Jinke Tang, Vladimir Golub Oct 2014

Magnetic And Transport Properties Of Nimnal Thin Films, Andriy Vovk, Minghui Yu, Leszek Malkinski, Charles O'Connor, Zhenjun Wang, Eden Durant, Jinke Tang, Vladimir Golub

Jinke Tang

The magnetic and transport properties of Ni2MnAl thin films prepared using pulse laser deposition were investigated. It was shown that the films are granular and multiphase. Contrary to the data reported earlier we observe nonmonotonic temperature dependence of resistance with minimum in the vicinity of 100 K for the films deposited on substrates held at 773 K and negative magnetoresistance (MR) values of about 2.5% at 5 K and 1.6% at RT in magnetic field of 50 kOe. These values of MR are the highest reported up to date for Ni2MnAl films. Large negative MR in …


4f Hybridization And Band Dispersion In Gadolinium Thin Films And Compounds, Takashi Komesu, H.-K. Jeong, David Wooton, Yaroslav B. Losovyj, J. N. Crain, M. Bissen, F. J. Himpsel, J. Petrosky, Jinke Tang, Wendong Wang, I. N. Yakovkin, Peter A. Dowben Oct 2014

4f Hybridization And Band Dispersion In Gadolinium Thin Films And Compounds, Takashi Komesu, H.-K. Jeong, David Wooton, Yaroslav B. Losovyj, J. N. Crain, M. Bissen, F. J. Himpsel, J. Petrosky, Jinke Tang, Wendong Wang, I. N. Yakovkin, Peter A. Dowben

Jinke Tang

There is interplay between intra-atomic orbital hybridization and extra-atomic hybridization in various gadolinium systems, which affects magnetic coupling and electron itinerancy (localization). The results do not always follow expectation. The experimental band structure of thin Gd(0001) films, grown on the Mo(112) surface, along the Γ − M does not agree with expectations even qualitatively. In particular, the dispersion of the gadolinium band, with strong 5d weight near 2 eV binding energy provides considerable evidence to support the case for 4f- 5d hybridization, with increasing 5d localization. On the other hand, there is also evidence of extra-atomic Gd 4f hybridization leading …


Magnetic Properties Of (Γ-Fe₂O₃)₈₀Ag₂₀ Nanocomposites Prepared In Reverse Micelles, Joan A. Wiemann, Jianbiao Dai, Jinke Tang, Gary J. Long, Leonard Spinu Oct 2014

Magnetic Properties Of (Γ-Fe₂O₃)₈₀Ag₂₀ Nanocomposites Prepared In Reverse Micelles, Joan A. Wiemann, Jianbiao Dai, Jinke Tang, Gary J. Long, Leonard Spinu

Jinke Tang

The magnetic properties of nanoparticles of gamma-Fe2O3 prepared by reverse micelles have been studied by dc magnetization, transverse ac susceptibility, and Mössbauer spectroscopy. The nanoparticles of gamma-Fe2O3 in the nanocomposite (gamma-Fe2O3)80Ag20 exhibit superparamagnetic behavior. The blocking temperatures determined by the three methods indicate the superparamagnetic nature of (gamma-Fe2O3)80Ag20 above 70-80 K and show correlation with measuring time. The average particle diameter obtained by transmission electron microscopy of the gamma-Fe2O3 particles is ~10 nm and that of the Ag particles is ~20 nm. The average particle size determined from the magnetic analyses for the gamma-Fe2O3 particles is ~12 nm. Mössbauer spectra …


Magnetic Properties Of (Γ-Fe₂O₃)₈₀Ag₂₀ Nanocomposites Prepared In Reverse Micelles, Joan Wiemann, Jianbiao Dai, Jinke Tang, Gary Long, Leonard Spinu Oct 2014

Magnetic Properties Of (Γ-Fe₂O₃)₈₀Ag₂₀ Nanocomposites Prepared In Reverse Micelles, Joan Wiemann, Jianbiao Dai, Jinke Tang, Gary Long, Leonard Spinu

Jinke Tang

The magnetic properties of nanoparticles of γ-Fe2O3 prepared by reverse micelles have been studied by dc magnetization, transverse ac susceptibility, and Mössbauer spectroscopy. The nanoparticles of γ-Fe2O3 in the nanocomposite (γ- Fe2 O3) 80Ag20 exhibit superparamagnetic behavior. The blocking temperatures determined by the three methods indicate the superparamagnetic nature of (γ- Fe2 O3) 80Ag20 above 70-80 K and show correlation with measuring time. The average particle diameter obtained by transmission electron microscopy of the γ-Fe2O3 particles is 10 nm and that of the Ag particles is 20 nm. The average particle size determined from the magnetic analyses for the γ-Fe2O3 …


Effect Of Gadolinium Doping On The Electronic Band Structure Of Europium Oxide, Juan Colon Santana, Joonhee Michael An, Ning Wu, Kirill Belashchenko, Xianjie Wang, Pan Liu, Jinke Tang, Yaroslav Losovyj, I. N. Yakovkin, Peter Dowben Oct 2014

Effect Of Gadolinium Doping On The Electronic Band Structure Of Europium Oxide, Juan Colon Santana, Joonhee Michael An, Ning Wu, Kirill Belashchenko, Xianjie Wang, Pan Liu, Jinke Tang, Yaroslav Losovyj, I. N. Yakovkin, Peter Dowben

Jinke Tang

High quality films of EuO and Eu0.96Gd0.04O were grown on p-type Si(100) via pulsed laser deposition. X-raydiffraction results show that the addition of Gd changes the growth texture from [001] to [111]. Angular-resolved photoemission spectroscopy reveals electron pockets around the X points in Gd-doped EuO, indicating that the band gap in EuO is indirect. Combined photoemission and inverse photoemission measurements showan apparent transition from n-type to p-type behavior, which is likely due to band bending near the polar (111) surface.


Tribological Properties Of Fullerenes C60 And C70 Microparticles, Wei Zao, Jinke Tang, Ashok Puri, Ray L. Sweany, Yuxin Li, Liquan Chen Oct 2014

Tribological Properties Of Fullerenes C60 And C70 Microparticles, Wei Zao, Jinke Tang, Ashok Puri, Ray L. Sweany, Yuxin Li, Liquan Chen

Jinke Tang

The frictional behaviors of fullerenes C60 and C70 were studied because they were speculated to be solid lubricants. For the sublimated pure C60 films on Si(001), a high friction coefficient (0.55–0.8) was observed under different loads and pin materials. For the C70 film, the friction coefficient showed a pin dependence, which changed from 0.5 with an Al2O3 pin to about 0.9 with a 440 stainless steel pin. The relatively high friction coefficients of C60 and C70 films were due to the tendency of the C60 and C70 particles to clump and compress into high shear strength layers rather than due …


The Electronic Structure Change With Gd Doping Of Hfo2 On Silicon, Yaroslav B. Losovyj, Ihor Ketsman, Andrei Sokolov, Kirill D. Belashchenko, Peter A. Dowben, Jinke Tang, Zhenjun Wang Oct 2014

The Electronic Structure Change With Gd Doping Of Hfo2 On Silicon, Yaroslav B. Losovyj, Ihor Ketsman, Andrei Sokolov, Kirill D. Belashchenko, Peter A. Dowben, Jinke Tang, Zhenjun Wang

Jinke Tang

Gd-doped HfO2 films deposited on silicon substrates undergo a crystallographic change from monoclinic to fluorite (cubic) phase with increasing Gd concentrations. The crystallographic phase change is accompanied by a small increase in the valence bandwidth and in the apparent band offset in the surface region. Electrical measurements show pronounced rectification properties for lightly doped Gd:HfO2 films on p-Si and for heavily-doped Gd:HfO2 films on n-Si, suggesting a crossover from n-type to p -type behavior with increasing doping level.


Enhanced Spin-Dependent Tunneling Magnetoresistance In Magnetite Films Coated By Polystyrene, Wendong Wang, Leszek Malkinski, Jinke Tang Oct 2014

Enhanced Spin-Dependent Tunneling Magnetoresistance In Magnetite Films Coated By Polystyrene, Wendong Wang, Leszek Malkinski, Jinke Tang

Jinke Tang

Hematite films were deposited by magnetron sputtering. A phase transformation from hematite to magnetite occurred when polystyrene (PS) coated hematite films were annealed above 200 °C in hydrogen flow. Giant negative magnetoresistance (MR) was observed with the best MR ratio of over 8% (at room temperature and in a field of 5.5 T) found in samples annealed at 230 °C. The temperature dependence of the resistivity is characteristic of intergranular tunneling. After the PS layer was removed and the films annealed again at 230 °C in hydrogen flow, the resistivity increased by about one order of magnitude and the MR …


Optimization Of The 3 M Tgm Beamline, At Camd, For Constant Initial State Spectroscopy, Yaroslav B. Losovyj, Ihor Ketsman, Eizi Morikawa, Zhenjun Wang, Jinke Tang, Peter A. Dowben Oct 2014

Optimization Of The 3 M Tgm Beamline, At Camd, For Constant Initial State Spectroscopy, Yaroslav B. Losovyj, Ihor Ketsman, Eizi Morikawa, Zhenjun Wang, Jinke Tang, Peter A. Dowben

Jinke Tang

The 3 m toroidal grating monochromator (TGM) VUV beamline at CAMD/LSU was realigned to achieve better illumination of the monochromator gratings with the goal of substantially increasing the flux at the higher photon energies. This is partly accomplished through a tilting of the monochromator (by about of 13.5°), with respect to the plane defined by the synchrotron, providing a smaller grazing angle at the initial mirrors. The improved performance of the beamline permits resonant photoemission studies at Gd 4d core threshold without resorting to second order light, which we demonstrate for Gd doped HfO2.


Comparison Of N-Type Gd2O3 And Gd-Doped Hfo2, Yaroslav B. Losovyj, David Wooten, Juan Colon Santana, Joonhee Michael An, Kirill D. Belashchenko, N. Lozova, J. C. Petrosky, Andrei Sokolov, Jinke Tang, Wendong Wang, Navamoney Arulsamy, Peter A. Dowben Oct 2014

Comparison Of N-Type Gd2O3 And Gd-Doped Hfo2, Yaroslav B. Losovyj, David Wooten, Juan Colon Santana, Joonhee Michael An, Kirill D. Belashchenko, N. Lozova, J. C. Petrosky, Andrei Sokolov, Jinke Tang, Wendong Wang, Navamoney Arulsamy, Peter A. Dowben

Jinke Tang

Gd2O3 and Gd-doped HfO2 films were deposited on p-type silicon substrates in a reducing atmosphere. Gd 4f photoexcitation peaks at roughly 7 and 5 eV below the valence band maximum have been identified using the resonant photoemission of Gd2O2 and Gd-doped HfO2 films, respectively. In the case of Gd2O3, strong hybridization with the O 2p band is demonstrated, and there is evidence that the Gd 4f weighted band exhibits dispersion in the bulk band structure. The rectifying (diode-like) properties of Gd-doped HfO2–silicon and Gd2O …


Gd-Doping Of Hfo2, Ihor Ketsman, Yaroslav B. Losovyj, Jinke Tang, Zhenjun Wang, M. L. Natta, Jennifer I. Brand, Peter A. Dowben Oct 2014

Gd-Doping Of Hfo2, Ihor Ketsman, Yaroslav B. Losovyj, Jinke Tang, Zhenjun Wang, M. L. Natta, Jennifer I. Brand, Peter A. Dowben

Jinke Tang

An increase in the density of states between the oxygen 2p bands and the Fermi level is seen with increasing Gd concentrations. In addition, for the Gd-doped HfO2 films, the Gd 4f photoexcitation peak at 5.5 eV below the valence band maximum was identified using resonant photoemission. Electrical measurements show pronounced rectification properties for lightly-doped Gd:HfO2 films on p-Si and for heavily-doped Gd:HfO2 films on n-Si, suggesting a crossover from n-type to p-type behavior with increasing doping level. In addition, there is an increase in the reverse bias current with neutron irradiation.


Ultrafine Nife2o4 Powder Fabricated From Reverse Microemulsion Process, Jiye Fang, Narayan Shama, Le Duc Tung, Eun Young Shin, Charles J. O'Connor, Kevin L. Stokes, Gabriel Caruntu, John B. Wiley, Leonard Spinu, Jinke Tang Oct 2014

Ultrafine Nife2o4 Powder Fabricated From Reverse Microemulsion Process, Jiye Fang, Narayan Shama, Le Duc Tung, Eun Young Shin, Charles J. O'Connor, Kevin L. Stokes, Gabriel Caruntu, John B. Wiley, Leonard Spinu, Jinke Tang

Jinke Tang

NiFe2O4 ultrafine powder with high crystallinity has been prepared through a reverse microemulsion route. The composition in starting solution was optimized, and the resulting NiFe2O4 was formed at temperature of around 550–600 °C, which is much lower than that observed from the solid-state reaction. Magnetic investigation indicates that samples are soft-magnetic materials with low coercivity and with the saturation magnetization close to the bulk value of Ni ferrite.