Prof. Sanghoon Lee
Prof. Sanghoon Lee
Korea University, Republic of Korea
Title: Magnetization switching in GaMnAs film by current induced spin orbit field in the absence of external field
Recently, the presence of current induced spin orbit magnetic fields (SO-field) was discovered in a crystalline ferromagnetic film, in which inversion symmetry is broken either by crystal structure itself or by strain. In this presentation, we experimentally demonstrate that the this SO-field can be used to switch magnetization in GaMnAs film. We have chosen to use a planar Hall resistance (PHR) measurement, which is sensitive to the direction of magnetization, to investigate the effect of the SO-field on the reorientation of magnetization. A1000 x 50 μm2 Hall device was fabricated from a 50 nm thick GaMnAs film. We have used 3.48 mA current pulses, which corresponds to a current density of 1.4 x 105 A/cm2, to switch magnetization. A 3s current pulse was strong enough to gnerate SO-field, which can reorient the direction of magnetization in GaMnAs film. This large current also reduces magnetic anisotroy energy of the GaMnAs film, making favorable condition for the magnetization switching, via Joule heating that increases temperature of the GaMnAs film. Owing to these two effects, the magnetization of the GaMnAs film was switched just by applying oppposite polarities of current pulse in the abscence of external field. Such magnetization switching was monitored by using a sensing current of 0.5 mA, which is small enough not to generate neither SO-field nor Joule heating. The result clearly demonstrates that the magnetization of GaMnAs film can be controlled only by current pulse, which provides significant advantage for the application of spintronic devices.
Sanghoon Lee obtained his B.S degree in physics from Korea University, Seoul, in 1987; and his Ph.D. degree in magnetic semiconductor physics at University of Notre Dame in 1996. After spending three years as a Postdoctoral Research Associate at physics department in University of Notre Dame (1997-1999), he joined the Electrical Materials Engineering Department at Kwangwoon University as a faculty member (2000). At Kwangwoon University he founded “spin functional semiconductor research center” supported by creative research initiative program. In 2001 he joined to Korea University as an assistant professor. He was promoted to the rank of Professor in 2008. His current research focuses on the spin related phenomena in semiconductor nanostructures, which include magnetic semiconductor materials growth, characterization of spin property, and semiconductor spin devices. Prof. Lee is the author or co-author of over 170 publications in SCI journals, mostly in the area of spin phenomena in semiconductors and magnetic materials. Sanghoon Lee is a member of the Korean academy of science and technology and the member of Korean Physics society. Sanghoon Lee was a member of Program Committees of at several international conferences on semiconductor nanostructures and/or spin-electronic effects in solids. Sanghoon Lee collaborates with colleagues in at least 10 other institutions, and has provided measurement techniques and intellectual input toward Ph.D. theses of over 10 graduate students in institutions other than his own.Last two year, he has served as department chair and the Director of BK21 plus project. He has served as an editor for one of SCI journals “Current Applied Physics” published by Elsevier from 2015-2017.