Distinct Detection of Thermally Induced Spin Voltage in Pt/WS₂/Ni₈₁Fe₁₉ by the Inverse Spin Hall Effect

Dastgeer, Ghulam,Shehzad, Muhammad Arslan,Eom, Jonghwa American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.51

<P>Conversion of heat into a spin current by means of the spin Seebeck effect (SSE) is one of the exciting topics in spin caloritronics. By use of this technique, the excess heat may be transformed into a valuable electric voltage by coupling SSE with the inverse spin Hall effect (ISHE). In this study, a thermal gradient and an in-plane magnetic field are used as the driving power to mobilize the spin electrons to produce SSE. A spin voltage is detected by ISHE in the Ni<SUB>81</SUB>Fe<SUB>19</SUB> heterostructure by means of a WS<SUB>2</SUB>/Pt strip. Using WS<SUB>2</SUB> sheets of different thicknesses, we obtained a large spin Seebeck coefficient of 0.72 μV/K, which is 12 times greater than the conventional spin Seebeck coefficient observed in Pt/Ni<SUB>81</SUB>Fe<SUB>19</SUB> bilayer devices. We observe the thickness dependence of tungsten disulfide (WS<SUB>2</SUB>) flakes and the polarity reversal of pure SSE signals that are measured without influence from the other thermoelectric effects in our Pt/WS<SUB>2</SUB>/Ni<SUB>81</SUB>Fe<SUB>19</SUB> device-the most intriguing feature of this study. Without the electric charge conduction, the spins are distributed over a longer distance that is greater than the spin diffusion length of the Ni<SUB>81</SUB>Fe<SUB>19</SUB> layer. Such features are strongly desired for designing the efficient spin-caloritronics devices that may be used in the thermoelectric spin generators and the temperature sensors such as thermocouples.</P> [FIG OMISSION]</BR>

Spin-orbit torques induced by spin Hall and spin swapping currents of a separate ferromagnet in a magnetic trilayer

박은상,민병철,구현철,김경완,이경진 한국물리학회 2021 Current Applied Physics Vol.29 No.-

Spin-orbit torques (SOTs) have been investigated most widely in normal metal/ferromagnet bilayers where the spin Hall effect of normal metal is a main source of spin currents. Recently, ferromagnets are found to also serve as spin-current sources through spin-orbit coupling. In this work, we theoretically investigate SOT acting on ferromagnet2 in ferromagnet1/normal metal/ferromagnet2 trilayers, which is caused by the spin Hall and spin swapping effects of ferromagnet1. Our result provides an analytical expression of SOT in the trilayers, which may be useful for quantifying the spin Hall and spin swapping effects of ferromagnets and also for designing and interpreting SOT experiments where a ferromagnet is used as a spin-current source instead of a normal metal.

Electrical Detection of the Spin Hall Effect in a Two-Dimensional Electron Gas

Seonn-Gu Huh,엄종화,구현철,한석희 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.1

The spin Hall effect has been investigated for an InAs heterostructure that provides a high-mobility two-dimensional electron gas. Due to the spin Hall effect, the motion of the spin-polarized electrons is curved and gives rise to a charge accumulation at the edge of the InAs channel. This charge accumulation induces a transverse voltage in the absence of an external magnetic field. We estimated the spin Hall sheet conductance of the InAs heterostructure to be 7.2 × 10-4 Ω-1 from the observed transverse voltage at 1.8 K. The magnitude of the spin Hall conductance indicates that the spin Hall effect observed in this experiment originates from an extrinsic origin rather than an intrinsic band structure.

Nonlocal Spin Diffusion Driven by Giant Spin Hall Effect at Oxide Heterointerfaces

Jin, Mi-Jin,Moon, Seon Young,Park, Jungmin,Modepalli, Vijayakumar,Jo, Junhyeon,Kim, Shin-Ik,Koo, Hyun Cheol,Min, Byoung-Chul,Lee, Hyun-Woo,Baek, Seung-Hyub,Yoo, Jung-Woo American Chemical Society 2017 NANO LETTERS Vol.17 No.1

<P>A two-dimensional electron gas emerged at a LaAlO3/SrTiO3 interface is an ideal system for 'spin-orbitronics' as the structure itself strongly couple the spin and orbital degree of freedom through the Rashba spin orbit interaction. One of core experiments toward this direction is the nonlocal spin transport measurement, which has remained elusive due to the low spin injection efficiency to this system. Here we bypass the problem by generating a spin current not through the spin injection from outside but instead through the inherent spin Hall effect and demonstrate the nonlocal spin transport. The analysis on the nonlocal spin voltage, confirmed by the signature of a Larmor spin precession and its length dependence, displays that both D'yakonov-Perel' and Elliott-Yafet mechanisms involve in the spin relaxation at low temperature. Our results show that the oxide heterointerface is highly efficient in spin-charge conversion with exceptionally strong spin Hall coefficient gamma similar to 0.15 +/- 0.05 and could be an outstanding platform for the study of coupled charge and spin transport phenomena and their electronic applications.</P>

Large spontaneous Hall angle in [Co, CoFe/Pt] multilayer

이하나,Y.J. Cho,엄종화,S.J. Joo,신경호,김태완 한국물리학회 2010 Current Applied Physics Vol.10 No.2

We have quantitatively investigated the Hall effect in [Co, CoFe/Pt] multilayer films. The [Co, CoFe/Pt]multilayers exhibit large spontaneous Hall resistivity (ρH) and Hall angle (ρH/ρ). Even though the Hall resistivity in [Co, CoFe/Pt] multilayer films (2.7–4 × 10-7 Ω cm) is smaller than that of amorphous RE–TM alloy films which show large spontaneous Hall resistivity (<2 × 10-6 Ω cm), the Hall angle of multilayer (6–8%) is almost twice than that in amorphous rare earth–transition metal alloy films (~3%). The Hall angle provides evidence of the effects of the exchange interaction of the Hall scattering. The exchange is between conduction electron spins and the localized spins of the transition metal. The large Hall angle of [Co, CoFe/Pt] multilayer can be considered due to the high spin polarization and high Curie temperature of Co and CoFe transition metal layers. Even though the role of interfaces and surfaces in the magnetic properties of multilayer films may dominate that of the bulk, the Hall effects in [Co, CoFe/Pt]multilayer may be mainly dominated by the bulk effect.

The observation of inherent spin Seebeck effect in Rh/YIG hybrid str

Fida Mohmed,Yuan-Hua Lin 한국물리학회 2019 Current Applied Physics Vol.19 No.4

Rhodium (Rh) is a 4d metal possessing a large spin orbit coupling strength and spin-Hall conductivity with a very small magnetic susceptibility, implying an insignificant magnetic proximity effect (MPE). We report here the observation of longitudinal spin Seebeck effect (LSSE) using Rh as a normal metal. A Rh film was sputtered on nanometer thick YIG films of highly crystalline nature and extremely low magnetic damping to obtain Rh/YIG hybrid structure. A clear thermal voltage Vth (SSE voltage) was obtained when a temperature gradient was applied on the Rh/YIG hybrid. The Rh film showed a very weak anomalous Hall resistance and the magnetoresistive testing clearly ruled out the magnetization of the Rh films via MPE. The anisotropic magnetoresistance (AMR) revealed a clear spin hall magnetoresistance (SMR) signal in Rh film implying a purely intrinsic spin current generation, free from any parasitic magnetic effects. The work can open a new window in the study of pure and uncontaminated spin current, generated in ferromagnetic insulators, using Rh as spin current detector.

Cr 기반의 이종박막 내에서 발생하는 오비탈 수송현상에 대한 연구

박은강,이년종,정세엽,김상훈,강민구,이수길,박병국,김우진 한국자기학회 2023 韓國磁氣學會誌 Vol.33 No.2

Spin-orbitronics devices based on spin Hall effect is a strong candidate for new generation memory devices. To realize this device the bilayer structure composed of a ferromagnet and a heavy metal layer should show sizable spin-orbit torque to manipulate magnetization of the devices. In this study, we investigate orbital transport in Cr-based heterostructures, because Cr has sizable orbital Hall angle and good conductivity. We found that orbital Hall magnetoresistance shows strong Cr-thickness dependence with the obtained diffusion length ~3 nm. Through a comparative experiment with the Cr/Pt/CoFeB structure in which the Pt layer was inserted, the orbital-spin conversion phenomenon by spin-orbit coupling can be understood. This study provides important information about orbital-related transport phenomenon in the Cr layer.

Effects of Mechanical Rotation and Vibration on Spin Currents

Mamoru Matsuo,Jun’ichi Ieda,Sadamichi Maekawa,Eiji Saitoh 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10

We discuss theoretically the generation of spin currents in both rotationally and linearly accelerated systems. The spin-orbit interaction modified by inertial effects is derived from the low energy limit of the generally covariant Dirac equation. It is shown that the spin-orbit interaction is responsible for the generation of spin currents by mechanical rotation and vibration. We also study effects of impurity scattering on the mechanically induced spin current, and calculate the spin accumulation by solving the spin diffusion equation with the spin-source term originating from the inertial effects.

Spin Hall Effect Induced by a Pd/CoFe Multilayer in a Semiconductor Channel

구현철,Jin-Seock Ma,장준연,김형준,한석희,엄종화,김철우 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

The spin Hall effect is observed for an InAs-based two-dimensional electron gas. Due to the spin Hall effect, the motion of the spin-polarized electrons deviates and causes a charge accumulation at the edge of the InAs channel. A spin imbalance between spin up and down is induced by spin injection from the Pd/CoFe multilayer, which is perpendicularly magnetized. This charge accumulation induces a transverse voltage in the absence of an external magnetic field. The observed spin Hall voltage decreases with increasing temperature and shows the same tendency as the spin diffusion length.

Spin Hall Effect-based Nonvolatile Flip Flop for Fine-grained Power Gating

Kon-Woo Kwon 대한전자공학회 2019 IEIE Transactions on Smart Processing & Computing Vol.8 No.5

This paper presents a nonvolatile flip flop (NVFF) for fine-grained power gating with data retention. The proposed NVFF exploits the spin Hall effect (SHE) for low-power and highspeed data backup operations. In order to evaluate the performance of the proposed NVFF, a simulation framework was used that consists of a SPICE circuit simulator and a Landau-Lifshitz-Gilbert solver. This work investigates the effect of process variation on the backup-and-restore operations, and shows that the proposed NVFF can achieve <5ns backup and <2ns restore operations even under process variations in the transistor and spin Hall device. Compared to the conventional spin transfer torque–based NVFF, the proposed NVFF improves the break-even time by more than three times because of the high spin injection efficiency of SHE and the simple single-phase backup mechanism.