Papers by Author: S.H. Han

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Authors: B.S. Moon, S.H. Han, I.K. Hwang, Young Hee Cho, C.E. Chung
Authors: M.H. Ham, Min Chang Jeong, W.Y. Lee, Jae Min Myoung, J.M. Lee, J.Y. Chang, S.H. Han
Abstract: We present the ferromagnetism and magnetotransport properties in the (Ga,Mn)N epitaxial films with very low Mn concentrations grown by plasma-enhanced molecular beam epitaxy (PEMBE). The (Ga,Mn)N epitaxial films were found to exhibit ferromagnetic ordering with Curie temperature of 700 K. All the films exhibit n-type characteristics. The negative magnetoresistance was observed below 150 K, and found to gradually increase with decreasing temperature. The ferromagnetism in the (Ga,Mn)N is due to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the localized Mn moments mediated by the electron gas.
Authors: Woong Joon Hwang, H.J. Lee, K.I. Lee, J.M. Lee, J.Y. Chang, S.H. Han, Y.K. Kim, W.Y. Lee, Moo Whan Shin
Abstract: The spin transport in a lateral spin-injection device with an FeCo/Si/FeCo junction has been investigated. Magnetoresistance (MR) signals were found to appear at low magnetic fields in the range 4 – 300 K. This is attributable to the switching of the magnetization of the two ferromagnetic contacts in the device for certain magnetic fields over which the magnetization in one contact is aligned antiparallel to that in the other. Our results suggest that the spin-polarized electrons are injected from the first contact and, after propagating through the bulk Si, are collected by the second contact.
Authors: K.I. Lee, M.H. Jeun, J.M. Lee, J.Y. Chang, S.H. Han, J.G. Ha, W.Y. Lee
Abstract: The magnetotransport properties of the electroplated and sputtered Bi thin films have been investigated in the range 4 – 300 K. A marked increase from 5,200 % to 80,000 % in the ordinary magnetoresistance (MR) for the electroplated Bi thin film was observed after thermal anneal at 4 K. The MR ratios for the as-grown and the annealed Bi thin films were found to exhibit 560 % and 590 %, respectively, at 300 K. On the other hand, the MR for the sputtered Bi film grown by sputtering was hardly observed at 4 and 300 K, whereas the MR ratios after anneal were found to reach 30,000 % at 4 K and 600 % at 300 K. We find that the room temperature MR in the sputtered films depends on the trigonal-axis oriented microstructures and grain size, in contrast to the electroplated films. Our results demonstrate the very large room temperature MR in the electroplated and sputtered Bi thin films, which can be used for spintronic device applications.
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