scholarly journals Spin–orbit torque engineering in β-W/CoFeB heterostructures with W–Ta or W–V alloy layers between β-W and CoFeB

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Gyu Won Kim ◽  
Do Duc Cuong ◽  
Yong Jin Kim ◽  
In Ho Cha ◽  
Taehyun Kim ◽  
...  
Keyword(s):  
Metal Layer ◽  
Spin Current ◽  
Hall Conductivity ◽  
Spin Orbit ◽  
Semiconductor Processing ◽  
Spintronic Devices ◽  
New Material ◽  
Switching Efficiency ◽  
Structure Calculations ◽  
Spin Hall Conductivity

AbstractThe spin–orbit torque (SOT) resulting from a spin current generated in a nonmagnetic transition metal layer offers a promising magnetization switching mechanism for spintronic devices. To fully exploit this mechanism, in practice, materials with high SOT efficiencies are indispensable. Moreover, new materials need to be compatible with semiconductor processing. This study introduces W–Ta and W–V alloy layers between nonmagnetic β-W and ferromagnetic CoFeB layers in β-W/CoFeB/MgO/Ta heterostructures. We carry out first-principles band structure calculations for W–Ta and W–V alloy structures to estimate the spin Hall conductivity. While the predicted spin Hall conductivity values of W–Ta alloys decrease monotonically from −0.82 × 103 S/cm for W100 at% as the Ta concentration increases, those of W–V alloys increase to −1.98 × 103 S/cm for W75V25 at% and then gradually decrease. Subsequently, we measure the spin Hall conductivities of both alloys. Experimentally, when β-W is alloyed with 20 at% V, the absolute value of the spin Hall conductivity considerably increases by 36% compared to that of the pristine β-W. We confirm that the W–V alloy also improves the SOT switching efficiency by approximately 40% compared to that of pristine β-W. This study demonstrates a new material that can act as a spin current-generating layer, leading to energy-efficient spintronic devices.

scholarly journals Efficient conversion of orbital Hall current to spin current for spin-orbit torque switching

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Soogil Lee ◽  
Min-Gu Kang ◽  
Dongwook Go ◽  
Dohyoung Kim ◽  
Jun-Ho Kang ◽  
...  
Keyword(s):  
Hall Effect ◽  
Spin Current ◽  
Orbit Coupling ◽  
Recent Theory ◽  
Spin Torque ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Spintronic Devices ◽  
Electric Generation ◽  
Switching Efficiency

AbstractSpin Hall effect, an electric generation of spin current, allows for efficient control of magnetization. Recent theory revealed that orbital Hall effect creates orbital current, which can be much larger than spin-Hall-induced spin current. However, orbital current cannot directly exert a torque on a ferromagnet, requiring a conversion process from orbital current to spin current. Here, we report two effective methods of the conversion through spin-orbit coupling engineering, which allows us to unambiguously demonstrate orbital-current-induced spin torque, or orbital Hall torque. We find that orbital Hall torque is greatly enhanced by introducing either a rare-earth ferromagnet Gd or a Pt interfacial layer with strong spin-orbit coupling in Cr/ferromagnet structures, indicating that the orbital current generated in Cr is efficiently converted into spin current in the Gd or Pt layer. Our results offer a pathway to utilize the orbital current to further enhance the magnetization switching efficiency in spin-orbit-torque-based spintronic devices.

scholarly journals Giant facet-dependent spin-orbit torque and spin Hall conductivity in the triangular antiferromagnet IrMn3

2016 ◽  
Vol 2 (9) ◽  
pp. e1600759 ◽  
Author(s):  
Weifeng Zhang ◽  
Wei Han ◽  
See-Hun Yang ◽  
Yan Sun ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Spin Current ◽  
Ferromagnetic Material ◽  
Hall Conductivity ◽  
Spin Torque ◽  
Spin Orbit ◽  
Intrinsic Mechanism ◽  
Efficient Charge ◽  
Field Annealing ◽  
Experimental Findings ◽  
Spin Hall Conductivity

There has been considerable interest in spin-orbit torques for the purpose of manipulating the magnetization of ferromagnetic elements for spintronic technologies. Spin-orbit torques are derived from spin currents created from charge currents in materials with significant spin-orbit coupling that propagate into an adjacent ferromagnetic material. A key challenge is to identify materials that exhibit large spin Hall angles, that is, efficient charge-to-spin current conversion. Using spin torque ferromagnetic resonance, we report the observation of a giant spin Hall angle θSHeff of up to ~0.35 in (001)-oriented single-crystalline antiferromagnetic IrMn3 thin films, coupled to ferromagnetic permalloy layers, and a θSHeff that is about three times smaller in (111)-oriented films. For (001)-oriented samples, we show that the magnitude of θSHeff can be significantly changed by manipulating the populations of various antiferromagnetic domains through perpendicular field annealing. We identify two distinct mechanisms that contribute to θSHeff: the first mechanism, which is facet-independent, arises from conventional bulk spin-dependent scattering within the IrMn3 layer, and the second intrinsic mechanism is derived from the unconventional antiferromagnetic structure of IrMn3. Using ab initio calculations, we show that the triangular magnetic structure of IrMn3 gives rise to a substantial intrinsic spin Hall conductivity that is much larger for the (001) than for the (111) orientation, consistent with our experimental findings.

scholarly journals Relation between the spin Hall conductivity and the spin Chern number for Dirac-like systems

2016 ◽  
Vol 13 (01) ◽  
pp. 1550136 ◽  
Author(s):  
Ömer F. Dayi ◽  
Elif Yunt
Keyword(s):  
Hall Effect ◽  
Chern Number ◽  
Hall Conductivity ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Quantum Level ◽  
Coupling Term ◽  
Physical Systems ◽  
Rashba Spin ◽  
Spin Hall Conductivity

A semiclassical formulation of the spin Hall effect for physical systems satisfying Dirac-like equation is introduced. We demonstrate that the main contribution to the spin Hall conductivity is given by the spin Chern number whether the spin is conserved or not at the quantum level. We illustrated the formulation within the Kane–Mele model of graphene in the absence and in the presence of the Rashba spin-orbit coupling term.

scholarly journals Quantization of spin Hall conductivity in two-dimensional topological insulators versus symmetry and spin-orbit interaction

2019 ◽  
Vol 100 (24) ◽  
Author(s):  
Filipe Matusalem ◽  
Marcelo Marques ◽  
Lara K. Teles ◽  
Lars Matthes ◽  
Jürgen Furthmüller ◽  
...  
Keyword(s):  
Topological Insulators ◽  
Orbit Interaction ◽  
Hall Conductivity ◽  
Spin Orbit ◽  
Two Dimensional ◽  
Spin Orbit Interaction ◽  
Spin Hall Conductivity

scholarly journals Spin supercurrent in two-dimensional superconductors with Rashba spin-orbit interaction

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
James Jun He ◽  
Kanta Hiroki ◽  
Keita Hamamoto ◽  
Naoto Nagaosa
Keyword(s):  
Chemical Potential ◽  
Spin Current ◽  
Orbit Interaction ◽  
Spin Orbit ◽  
Two Dimensional ◽  
Spin Orbit Interaction ◽  
Spintronic Devices ◽  
Rashba Spin ◽  
Normal States ◽  
Dilute Limit

Abstract Spin current is a central theme in spintronics, and its generation is a keen issue. The spin-polarized current injection from the ferromagnet, spin battery, and spin Hall effect have been used to generate spin current, but Ohmic currents in the normal state are involved in all of these methods. On the other hand, the spin and spin current manipulation by the supercurrent in superconductors is a promising route for dissipationless spintronics. Here we show theoretically that, in two-dimensional superconductors with Rashba spin-orbit interaction, the generation of dissipationless bulk spin current by charge supercurrent becomes highly efficient, exceeding that in normal states in the dilute limit, i.e. when the chemical potential is close to the band edge, although the spin density becomes small there. This result manifests the possibility of creating new spintronic devices with long-range coherence.

scholarly journals Spin transport in insulators without exchange stiffness

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Koichi Oyanagi ◽  
Saburo Takahashi ◽  
Ludo J. Cornelissen ◽  
Juan Shan ◽  
Shunsuke Daimon ◽  
...  
Keyword(s):  
Spin Transport ◽  
Spin Diffusion ◽  
Spin Current ◽  
Material Design ◽  
Magnetic Films ◽  
Design Strategies ◽  
Spintronic Devices ◽  
Spin Currents ◽  
New Material ◽  
Conventional Models

Abstract The discovery of new materials that efficiently transmit spin currents has been important for spintronics and material science. The electric insulator Gd3Ga5O12 (GGG), a standard substrate for growing magnetic films, can be a spin current generator, but has never been considered as a superior conduit for spin currents. Here we report spin current propagation in paramagnetic GGG over several microns. Surprisingly, spin transport persists up to temperatures of 100 K $$\gg$$ ≫ Tg = 180 mK, the magnetic glass-like transition temperature of GGG. At 5 K and 3.5 T, we find a spin diffusion length λGGG = 1.8 ± 0.2 μm and a spin conductivity σGGG = (7.3 ± 0.3) × 104 Sm−1 that is larger than that of the record quality magnet Y3Fe5O12 (YIG). We conclude that exchange stiffness is not required for efficient spin transport, which challenges conventional models and provides new material-design strategies for spintronic devices.

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