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Spin-orbit torque engineering by orbital current in Cr-based magnetic heterostructures
Soogil Lee,Min-Gu Kang,Dongwook Go,Taekhyeon Lee,Dohyoung Kim,Geun-Hee Lee,Jun-Ho Kang,Jong-Ryul Jeong,Kyung-Jin Lee,Hyun-Woo Lee,Kab-Jin Kim,Sanghoon Kim,Byong-Guk Park 한국자기학회 2020 한국자기학회 학술연구발표회 논문개요집 Vol.30 No.1
Giant Spin-orbit Torques Induced by Orbital Hall Effect
Soogil Lee,Junho Kang,Taekhyeon Lee,Jung-Mok Kim,Dohyoung Kim,Heechan Jang,Eun Kang Park,Dongwook Go,Nyun Jong Lee,Yoshinori Kotani,Yoichi Shiota,Teruo Ono,S. Sonny Rhim,Kyung-Jin Lee,Hyun-Woo Lee,Kab 한국자기학회 2019 한국자기학회 학술연구발표회 논문개요집 Vol.29 No.2
Soogil Lee,Jaimin Kang,Jeong-Mok Kim,Taek-Hyeon Lee,Sungjun Lee,Donghyeon Han,Sanghwa Lee,Kab-Jin Kim,Byong-Guk Park 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
Entering the era of Inter of Things (IOT), diverse smart devices generate and transfer enormous digital information. In this IOT environment, information security is becoming a critical issue because conventional software-based security technology is vulnerable to adversarial machine learning attacks. Thus, hardware-based security technology has been proposed to overcome this vulnerability, receiving much attention as an alternative. Especially, randomness of nature serves as an essential ingredient for the hardware-based security technology. For example, manufacturing processes of complementary-metal-oxide-semiconductor (CMOS) involves inevitable tolerances. Therefore, every electronic device is physically not identical despite the identical manufacturing processes. Those distinguishable device characteristics under the identical manufacturing process, so called “physical unclonable function (PUF)”, can potentially create non-identical output (response) under the identical input (challenge) generating unique identification of each electronic devices [1]. In this presentation, we demonstrate the spintronic PUF utilizing bottom-ferromagnet (FM)/nonmagnet/top-FM trilayer structures. Here, bottom and top FMs exhibit in-plane and perpendicular magnetic anisotropy, respectively. In these trilayer structures, field-free magnetization switching of top-FM is achieved by out-of-plane polarized spin current injection due to the interfacial spin precession mechanism, and the switching polarity is controlled by the in-plane magnetization direction of bottom-FM [2]. Under the identical demagnetization process of the bottom-FM, distinct magnetic domain distributions are formed on each identical wafer, consisting of a number of Hall-bar devices with random magnetization direction of bottom-FM along the demagnetization axis. These randomly distributed domains of bottom-FM on each wafer are electrically detected through the current-induced field-free spin-orbit torque switching polarity relies on the direction of bottom-FM. Therefore, these spintronic PUF wafers with unique pattern of domain distributions manifests itself as the unique electrical identification which can also be integrated into magnetic random access memory. Furthermore, we also discuss the reconfigurability and reliability of this spintronic PUF, providing great potential to hardware-based security applications because it is compatible with current CMOS technology.
Sukjin Choi,Sangjin Lee,Kideok Sim,Jeonwook Cho,Soogil Lee,Sang-Geun Lee,Kyu Won Lee,Sang Young Lee,Dong Ho Kim,Tae Kuk Ko IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>In Korea, the superconducting power cable has been developed since 2001, with the basic specifications of 22.9 kV/50 MVA. The superconducting power cable can carry more than 2 to 5 times higher electric power compared with conventional ones. It is important to test the DC critical current related with its power capacity before applying to the real power grid. In 1995, several international standards organizations including IEC, decided to unify the use of statistical terms related with 'accuracy' or 'precision' in their standards. It was decided to use the word 'uncertainty' for all quantitative (associated with a number) statistical expressions. In this paper, we measured DC critical current of 22.9 kV/50 MVA superconducting power cable with several voltage tap and analyzed the uncertainty with these results. These analyzed results can be applied the standardization of the superconducting power cable.</P>
Lee, Soogil,Han, Yoonsung,Kim, Sanghoon,Hong, Jongill American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.105 No.7
<P>By investigating angular dependence of resistance and applying the Boltzmann distribution to the anisotropy dispersion of the magnetization in an exchange-biased pinned layer, we quantized the intrinsic anisotropy dispersion sigma(gamma) of spin valves. The sigma(gamma) was estimated to be 0.412 degrees for the as-deposited spin valve and 0.183 degrees for the ion-irradiated spin valve. This indicates that the dispersion indeed narrowed when the spin valve was field-annealed or irradiated by 550 eV hydrogen ions under a magnetic field, which is consistent with our previous attribution to the significant improvement in both exchange anisotropy and giant magnetoresistance of spin valves thus treated. Our methodology can be applied for other spin devices characterized by angular dependence of resistance to determine useful device properties such as the intrinsic anisotropy dispersion and the exchange bias of the exchange-biased reference layer. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3072776]</P>
Field-free spin-orbit torque switching of perpendicular magnetization
Soogil Lee,Byong-Guk Park 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2
Spin-orbit torque (SOT) arising from spin-orbit coupling has gained much attention because it promises efficient magnetization switching in spintronic devices. It is important for device applications that the SOT switches perpendicular magnetizations without an external magnetic field. In this talk, I will present two approaches to field-free SOT switching of perpendicular magnetization. First, we investigate SOT in antiferromagnet IrMn/CoFeB/MgO structures, where an in-plane effective field and a sizable SOT generated from IrMn can switch the magnetization perpendicular CoFeB without an external magnetic field. Second, we demonstrate that out-of-plane SOT created at a ferromagnet/non-magnetic interface deterministically switches magnetization in a magnetic trilayer.
비자성/강자성 이중층에서 스핀 궤도 돌림힘의 전기적 측정방법 고찰
이수길(Soogil Lee),류정춘(Jeongchun Ryu),최종국(Jong-Guk Choi),김정목(Jeong-Mok Kim),이재욱(Jae Wook Lee),박준영(June-Young Park),강재민(Jaimin Kang),박병국(Byong-Guk Park) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.3
Spin-orbit torque (SOT) is a spin torque based on spin-orbit coupling in a nonmagnet/ferromagnet heterostructure. In this structure, transverse spin current that is generated by an in-plane charge current and exerts torque on the adjacent ferromagnetic layer. This is intensively investigated because it can be used to switch the ferromagnet effectively in various spintronic devices. Here, we discuss various experimental methods to evaluate the SOT in nonmagnet/ferromagnet bilayer structures.