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Your search keyword '"Jo, Young-Hun"' showing total 27 results
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27 results on '"Jo, Young-Hun"'

1. Effect of spin relaxation rate on the interfacial spin depolarization in ferromagnet/oxide/semiconductor contacts

Author

Jeon, Kun-Rok, Min, Byoung-Chul, Park, Youn-Ho, Jo, Young-Hun, Park, Seung-Young, Park, Chang-Yup, and Shin, Sung-Chul

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Combined measurements of normal and inverted Hanle effects in CoFe/MgO/semiconductor (SC) contacts reveal the effect of spin relaxation rate on the interfacial spin depolarization (ISD) from local magnetic fields. Despite the similar ferromagnetic electrode and interfacial roughness in both CoFe/MgO/Si and CoFe/MgO/Ge contacts, we have observed clearly different features of the ISD depending on the host SC. The precession and relaxation of spins in different SCs exposed to the local fields from more or less the same ferromagnets give rise to a notably different ratio of the inverted Hanle signal to the normal one. At room temperature, a large ISD is observed in the CoFe/MgO/Si contact, but a small ISD in the CoFe/MgO/Ge contact. The ISD of the CoFe/MgO/Ge contact has been substantially increased at low temperature. These results can be ascribed to the difference of spin relaxation in host SCs. A model calculation of the ISD, considering the spin precession due to the local field and the spin relaxation in the host SC, explains the temperature and bias dependence of the ISD consistently., Comment: 23 pages, 6 figures

Published
2011
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2. Electrical spin injection and accumulation in CoFe/MgO/Ge contacts at room temperature

Author

Jeon, Kun-Rok, Min, Byoung-Chul, Jo, Young-Hun, Lee, Hun-Sung, Shin, Il-Jae, Park, Chang-Yup, Park, Seung-Young, and Shin, Sung-Chul

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We first report the all-electrical spin injection and detection in CoFe/MgO/moderately doped n-Ge contact at room temperature (RT), employing threeterminal Hanle measurements. A sizable spin signal of ~170 k{\Omega} {\mu}m^2 has been observed at RT, and the analysis using a single-step tunneling model gives a spin lifetime of ~120 ps and a spin diffusion length of ~683 nm in Ge. The observed spin signal shows asymmetric bias and temperature dependences which are strongly related to the asymmetry of the tunneling process., Comment: 28 pages, 5 figures

Published
2011
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6. Fluctuation conductivity of single-crystalline BaFe1.8Co0.2As2 in the critical region.

Author

Kim, Soo Hyun, Choi, Chang Ho, Jung, Myung-Hwa, Yoon, Jung-Bum, Wang, X. F., Chen, X. H., Wang, X. L., Lee, Sung-Ik, Choi, Ki-Young, and Jo, Young-Hun

Subjects
CRYSTALS, BARIUM compounds, BARIUM, IRON, COBALT, FLUCTUATIONS (Physics), MEAN field theory, TRANSITION temperature
Abstract

The magnetofluctuation conductivity, called excess conductivity, originated from the forming of the superconducting droplet near to the mean-field transition temperature, was measured for the optimally doped BaFe1.8Co0.2As2 single crystals with a critical temperature, Tc, of 24.6 K. This measurement of the excess conductivity for magnetic fields up to 9 T was compared with the thermodynamic scaling theory in the critical region, in which not only the Gaussian fluctuation but also fourth order terms of the order parameter are included. An analysis of the excess conductivity showed that the superconductivity followed three-dimensional scaling rather than two-dimensional scaling even though the sample had a layered structure. [ABSTRACT FROM AUTHOR]

Published
2010
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7. A comparative study of the dendritic avalanche in MgB2 thin films synthesized by pulsed laser deposition and hybrid physical chemical vapor deposition methods.

Author

Lee, Jae-Yeap, Lee, Hu-Jong, Lee, Sung-Ik, Zhuang, C. G., Wang, Y. Z., Feng, Q. R., Gan, Z. Z., Xi, X. X., Choi, Eun-Mi, Cho, Jae-Hun, and Jo, Young-Hun

Subjects
THIN films, PULSED laser deposition, CHEMICAL vapor deposition, HYSTERESIS, SCANNING electron microscopy, CRITICAL currents, SUPERCONDUCTING quantum interference devices
Abstract

It is known that MgB2 thin films synthesized by using hybrid physical chemical vapor deposition (HPCVD) do not show dendritic avalanche, which is in contrast to those prepared by using pulsed laser deposition (PLD). To find the cause that makes the difference between the two cases, we studied the microscopic film structure by the scanning electron microscopy and the magnetic hysteresis by using the superconducting quantum interference device magnetometry. The critical current density (Jc), estimated from the magnetic hysteresis based on the Bean’s critical-state model, shows a much higher Jc in the PLD film than in a HPCVD film. This indicates higher vortex pinning in the PLD film. We surmise that high local joule heating beyond the high Jc in the PLD film, as a vortex penetrates into the superconducting thin film, gives a path for the next vortex and induces a positive feedback effect that is absent in the HPCVD film. [ABSTRACT FROM AUTHOR]

Published
2009
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8. Fluctuation conductivity of single-crystalline BaFe1.8 Co0.2As2 in the critical region

Author

Kim, Soo Hyun, Choi, Changho, Jung, Myung-Hwa, Yoon, Jung-Bum, Jo, Young-Hun, Wang, Xiaolin, Chen, X.H, Wang, X.F, Lee, Sung-Ik, Choi, Ki-Young, Kim, Soo Hyun, Choi, Changho, Jung, Myung-Hwa, Yoon, Jung-Bum, Jo, Young-Hun, Wang, Xiaolin, Chen, X.H, Wang, X.F, Lee, Sung-Ik, and Choi, Ki-Young

Abstract

The magnetofluctuation conductivity, called excess conductivity, originated from the forming of the superconducting droplet near to the mean-field transition temperature, was measured for the optimally doped BaFe1.8Co0.2As2 single crystals with a critical temperature, Tc, of 24.6 K. This measurement of the excess conductivity for magnetic fields up to 9 T was compared with the thermodynamic scaling theory in the critical region, in which not only the Gaussian fluctuation but also fourth order terms of the order parameter are included. An analysis of the excess conductivity showed that the superconductivity followed three-dimensional scaling rather than two-dimensional scaling even though the sample had a layered structure.

Published
2010

27. Characteristics of Ti0.97Co0.03O2:Sb0.01 dilute magnetic semiconducting thin films deposited at 500°C by pulsed laser deposition

Author

Seong, Nak-Jin, Jo, Young-Hun, Jung, Myung-Hwa, and Yoon, Soon-Gil

Subjects
*COATING processes, *PULSED laser deposition, *THICK films, *HALL effect
Abstract

Abstract: Epitaxial Ti0.97Co0.03O2:Sb0.01(TCO:Sb) films were deposited on R-Al2O3 (1102) substrates at 500°C in various deposition pressures by pulsed laser deposition. The solubility of cobalt within the films increases with decreasing deposition pressure at a deposition temperature of 500°C. The TCO:Sb films deposited at 5×10−6 Torr exhibit a p-type anomalous Hall effect having a hole concentration of 6.1×1022/cm3 at 300K. On the other hand, films deposited at 4×10−4 Torr exhibits an n-type anomalous Hall effect having an electron concentration of about 1.1×1021/cm3. p- or n-type DMS characteristics depends on the change of the structure of TCO:Sb films and the solubility of Co is possible by controlling the deposition pressure. [Copyright &y& Elsevier]

Published
2006
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