Mesoscopic spin Hall effect in multiprobe ballistic spin-orbit-coupled semiconductor bridges

AbstractThe orbital Hall effect describes the generation of the orbital current flowing in a perpendicular direction to an external electric field, analogous to the spin Hall effect. As the orbital current carries the angular momentum as the spin current does, injection of the orbital current into a ferromagnet can result in torque on the magnetization, which provides a way to detect the orbital Hall effect. With this motivation, we examine the current-induced spin-orbit torques in various ferromagnet/heavy metal bilayers by theory and experiment. Analysis of the magnetic torque reveals the presence of the contribution from the orbital Hall effect in the heavy metal, which competes with the contribution from the spin Hall effect. In particular, we find that the net torque in Ni/Ta bilayers is opposite in sign to the spin Hall theory prediction but instead consistent with the orbital Hall theory, which unambiguously confirms the orbital torque generated by the orbital Hall effect. Our finding opens a possibility of utilizing the orbital current for spintronic device applications, and it will invigorate researches on spin-orbit-coupled phenomena based on orbital engineering.

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Inactivation of damping-like torque in Tb-Gd-Fe film on Ta layer

Japanese Journal of Applied Physics ◽

10.35848/1347-4065/ac3fcb ◽

2021 ◽

Author(s):

Yuichiro Kurokawa ◽

Masahiro Itoh ◽

Masakazu Wakae ◽

Masahiro Fujimoto ◽

Uraku Kamihoki ◽

...

Keyword(s):

Rare Earth ◽

Transition Metal ◽

Hall Effect ◽

Effective Field ◽

Spin Hall Effect ◽

Spin Orbit

Abstract Recently, bulk spin orbit torques (SOTs) in transition metal-rare earth (TM-RE) ferrimagnets have been reported. In this study, to investigate bulk SOTs, we observed the current-induced effective field mediated by a damping-like torque (DLT), which is one of the components of SOTs, using TM-RE ferrimagnetic Tb x (Gd32Fe68)100-x films with a Ta layer. The DLT efficiency ξ DL was inactivated by increasing the Tb composition x to be greater than 8, suggesting that the DLT was induced by the bulk SOTs of Tb x (Gd32Fe68)100-x as well as the spin Hall effect in the Ta. However, from the DLT measurement using a Tb8(Gd32Fe68)92 layer sandwiched between Ru layers, where Ru has a negligibly small DLT, ξ DL was almost zero. This indicates that the inactivation of DLT cannot simply be explained by the bulk SOTs of Tb x (Gd32Fe68)100-x . However, we expect that this finding will provide meaningful insights for controlling magnetization using current.

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Disentanglement of Spin-Orbit Torques in Pt / Co Bilayers with the Presence of Spin Hall Effect and Rashba-Edelstein Effect

Physical Review Applied ◽

10.1103/physrevapplied.13.054014 ◽

2020 ◽

Vol 13 (5) ◽

Cited By ~ 2

Author(s):

Ye Du ◽

Hiromu Gamou ◽

Saburo Takahashi ◽

Shutaro Karube ◽

Makoto Kohda ◽

...

Keyword(s):

Hall Effect ◽

Spin Hall Effect ◽

Spin Orbit

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Robust spin–orbit torques in ferromagnetic multilayers with weak bulk spin Hall effect

Applied Physics Letters ◽

10.1063/5.0011399 ◽

2020 ◽

Vol 117 (12) ◽

pp. 122401

Author(s):

Q. B. Liu ◽

K. K. Meng ◽

S. Q. Zheng ◽

J. K. Chen ◽

J. Miao ◽

...

Keyword(s):

Hall Effect ◽

Spin Hall Effect ◽

Spin Orbit

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Understanding spin Hall effect in two-dimensional fermionic systems with generic spin–orbit interaction in III–V heterostructures

Physics Letters A ◽

10.1016/j.physleta.2014.11.060 ◽

2015 ◽

Vol 379 (7) ◽

pp. 728-731 ◽

Cited By ~ 1

Author(s):

Boudhayan Paul ◽

Tarun Kanti Ghosh

Keyword(s):

Hall Effect ◽

Orbit Interaction ◽

Spin Hall Effect ◽

Spin Orbit ◽

Two Dimensional ◽

Spin Orbit Interaction ◽

Fermionic Systems

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MAGNETO-GYROTROPIC PHOTOGALVANIC EFFECTS IN SEMICONDUCTOR QUANTUM WELLS

International Journal of Modern Physics B ◽

10.1142/s0217979208046189 ◽

2008 ◽

Vol 22 (01n02) ◽

pp. 115-116 ◽

Cited By ~ 1

Author(s):

S. D. GANICHEV

Keyword(s):

Hall Effect ◽

Electric Current ◽

Electron Gas ◽

Spin Hall Effect ◽

Orbit Coupling ◽

Relaxation Processes ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Wide Range ◽

Spin Dependent Scattering

The spin-orbit coupling provides a versatile tool to generate and to manipulate the spin degree of freedom in low-dimensional semiconductor structures. The spin Hall effect, where an electric current drives a transverse spin current and causes a nonequilibrium spin accumulation near the sample boundary,1,2 the spin-galvanic effect, where a nonequilibrium spin polarization drives an electric current3,4 or the reverse process, in which an electrical current generates a non-equilibrium spin-polarization,5–9 are all consequences of spin-orbit coupling. In order to observe a spin Hall effect a bias driven current is an essential prerequisite. Then spin separation is caused via spin-orbit coupling either by Mott scattering (extrinsic spin Hall effect) or by spin splitting of the band structure (intrinsic spin Hall effect). Recently an elementary effect causing spin separation which is fundamentally different from that of the spin Hall effect has been observed.10 In contrast to the spin Hall effect it does not require an electric current to flow: it is spin separation achieved by spin-dependent scattering of electrons in media with suitable symmetry. It is show that by free carrier (Drude) absorption of terahertz radiation spin separation is achieved in a wide range of temperatures from liquid helium temperature up to room temperature. Moreover the experimental results demonstrate that simple electron gas heating by any means is already sufficient to yield spin separation due to spin-dependent energy relaxation processes of non-equilibrium carriers. In order to demonstrate the existence of the spin separation due to asymmetric scattering the pure spin current was converted into an electric current. It is achieved by application of a magnetic field which polarizes spins. This is analogues to spin-dependent scattering in transport experiments: spin-dependent scattering in an unpolarized electron gas causes the extrinsic spin Hall effect, whereas in a spin-polarized electron gas a charge current, the anomalous Hall effect, can be observed. As both magnetic fields and gyrotropic mechanisms were used authors introduced the notation "magneto-gyrotropic photogalvanic effects" for this class of phenomena. The effect is observed in GaAs and InAs low dimensional structures at free-carrier absorption of terahertz radiation in a wide range of temperatures from liquid helium temperature up to room temperature. The results are well described by the phenomenological description based on the symmetry. Experimental and theoretical analysis evidences unumbiguously that the observed photocurrents are spin-dependent. Microscopic theory of this effect based on asymmetry of photoexcitation and relaxation processes are developed being in a good agreement with experimental data. Note from Publisher: This article contains the abstract only.

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