Universal Intrinsic Spin Hall Effect

Sinova, Jairo; Culcer, Dimitrie; Niu, Qian; Sinitsyn, Nikolai A.; Jungwirth, T.; MacDonald, Allan H.

doi:10.1103/physrevlett.92.126603

Cited by 2,126 publications

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References 36 publications

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“…Exotic quantum phases induced by the spin-orbit coupling have been attracting recent interest in various fields of condensed matter physics, owing to their fascinating phenomena such as noncentrosymmetric superconductivity, 1 chiral magnetism, 2, 3 multipole order, 4 multiferroics, 5 spintronics, 6,7 and topological quantum phases. [8][9][10] Intriguing properties appear in the electronic structure, transport, optics, magnetic excitation, and so forth, as a result of the spin-orbit coupling and symmetry breaking.…”

Section: Introductionmentioning

confidence: 99%

Electric Octupole Order in Bilayer Ruthenate Sr₃Ru₂O₇

Hitomi

Yanase

2014

J. Phys. Soc. Jpn.

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Although the odd-parity multipole order barely occurs in crystals with high symmetry, it can be formed in locally noncentrosymmetric crystals. We illustrate the odd-parity electric octupole order generated in a bilayer structure. When the local electric quadrupole is alternatively stacked between layers, it is regarded as an electric octupole order from the viewpoint of symmetry. We show that the p y s x + p x s y spin nematic order is induced by the spin-orbit coupling in the electric octupole state, and it results from the spontaneous inversion symmetry breaking leading to the D 2d point group symmetry. We investigate the possible realization of the electric octupole order in the bilayer ruthenate Sr 3 Ru 2 O 7 , assuming a local electric quadrupole arising from the Pomeranchuk instability and/or the orbital order. Effects of the lattice distortion and magnetic field are also clarified, and the nature of the "electronic nematic state" of Sr 3 Ru 2 O 7 is discussed. It is proposed that the asymmetric band structure is a signature of the electric octupole order in Sr 3 Ru 2 O 7 . The odd-parity multipole order in other strongly correlated electron systems is discussed.

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Section: Introductionmentioning

confidence: 99%

Electric Octupole Order in Bilayer Ruthenate Sr₃Ru₂O₇

Hitomi

Yanase

2014

J. Phys. Soc. Jpn.

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“…We present a new NM/F/I structure, which provides a novel spin-orbit torque, resulting in zero-field current-induced switching of perpendicular magnetization. Our device consists of a stack of Ta/Co 20 Fe 60 B 20 /TaO x layers, but also has a structural mirror asymmetry along the in-plane direction. The lateral structural asymmetry, in effect, replaces the role of the external in-plane magnetic field.…”

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Switching of perpendicular magnetization by spin–orbit torques in the absence of external magnetic fields

et al. 2014

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Breaking of structural symmetries of nanomagnetic systems is of great interest for the development of ultralow-power spintronic devices. The structural asymmetry in various magnetic heterostructures has been engineered to reveal novel fundamental interactions between electric currents and magnetization, resulting in spin-orbit-torques (SOTs) on the magnetization [1][2][3][4][5][6] , which are both fundamentally important and technologically promising for device applications. Such SOTs have been used to realize current-induced magnetization switching [2][3][4]7 and domain-wall 3 motion [8][9][10] in recent experiments. Typical heterostructures exhibiting SOTs consist of a ferromagnet (F) with a heavy nonmagnetic metal (NM) having strong spin-orbit coupling on one side, and an insulator (I) on the other side (referred to as NM/F/I structures, shown schematically in Fig. 1a, which break mirror symmetry in the growth direction). In terms of device applications, the use of SOTs in NM/F/I structures allows for a significantly lower write current compared to regular spin-transfer-torque (STT) devices 4 . It can greatly improve energy efficiency and scalability [1][2][3][4][5]11 for new SOT-based devices such as magnetic random access memory (SOT-MRAM), going beyond state-of-the-art STT-MRAM.For practical applications, a critical requirement to achieve high-density SOT memory is the ability to perform SOT-induced switching without the use of external magnetic fields, in particular for perpendicularly-magnetized ferromagnets, which show better scalability and thermal stability as compared to the in-plane case 12 .However, there are currently no practical solutions that meet this requirement. In NM/F/I heterostructures studied so far, the form of the resultant current-induced SOT alone does not allow for deterministic switching of a perpendicular ferromagnet, requiring application of an additional external in-plane magnetic field to switch the perpendicular magnetization [2][3][4] . (This is a very general feature of SOT devices, which can be explained by symmetry-based arguments, as discussed below). In such experiments, the external field allows for each current direction to favor a particular orientation for the out-of-plane component of magnetization, thereby resulting in deterministic perpendicular switching. However, this external field is undesirable 4 from a practical point of view. For device applications, it also reduces the thermal stability of the perpendicular magnet by lowering the zero-current energy barrier between the stable perpendicular states, resulting in a shorter retention time if used for memory.This work provides a solution to eliminate the use of external magnetic fields, bringing SOT-based spintronic devices such as SOT-MRAM closer to practical application. We present a new NM/F/I structure, which provides a novel spin-orbit torque, resulting in zero-field current-induced switching of perpendicular magnetization. Our device consists of a stack of Ta/Co 20 Fe 60 B 20 /TaO x layers, but also has a...

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“…The related spin-Hall effect, causing accumulations of spins at the edges, has also been observed [4]. It can be extrinsic, i.e., caused by impurities with SO scattering [5,6] or intrinsic due to an SO split band structure [7,8]. However, all experiments to date detected the current-induced spins optically [16].…”

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confidence: 99%

“…[13] for diffusion equations (Eqs. (6)(7)(8) in Ref. [13]) and for the expression of SC in terms of E (Eq.…”

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confidence: 99%

Detection of Current-Induced Spins by Ferromagnetic Contacts

2006

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Detection of current-induced spin accumulation via ferromagnetic contacts is discussed. Onsager's relations forbid that in a two-probe configuration, spins excited by currents in time-reversal symmetric systems can be detected by switching the magnetization of a ferromangetic detector contact. Nevertheless, current-induced spins can be transferred as a torque to a contact magnetization and can affect the charge currents in many-terminal configurations. We demonstrate the general concepts by solving the microscopic transport equations for the diffuse Rashba system with magnetic contacts. DOI: 10.1103/PhysRevLett.97.256601 PACS numbers: 72.25.Dc, 72.20.Dp, 72.25.Mk The notion that netto spin distributions can be generated by electric currents in the bulk of nonmagnetic semiconductors with intrinsic spin-orbit (SO) interaction has been predicted [1,2] and experimentally confirmed [3]. The related spin-Hall effect, causing accumulations of spins at the edges, has also been observed [4]. It can be extrinsic, i.e., caused by impurities with SO scattering [5,6] or intrinsic due to an SO split band structure [7,8]. However, all experiments to date detected the current-induced spins optically [16]. An important remaining challenge for theory and experiment is to find ways to transform the novel spin accumulation (SA) and spin currents (SCs) into voltage differences and charge currents in micro-or nanoelectronic circuits in order to fulfill the promises of spintronics.In this Letter, we address the possibility to generate a spin-related signal to be picked up by ferromagnetic contacts. This signal can be in the form of a voltage change or a torque acting on the magnetization of the ferromagnet (FM). In practice, this raises technical difficulties due the conductance mismatch [17] that can be solved [18] and are not addressed here. We rather focus on conceptual problems that are related to the voltage and torque signals generated by current-induced spins [19]. The Onsager relations for the conductance [20] forbid voltage based detection of current-induced spins by a ferromagnetic lead in a two-probe setup within linear response. We sketch a microscopic picture of the physics and formulate a semiclassical scheme in the diffuse limit. We address spin detection in a multiprobe geometry, calculate the Hall conductivity, and compare it to the anomalous Hall effect. We also discuss the possibility to construct spin filters not based on FMs, but on conductors with spatially modulated SO interactions.We first address the symmetry properties in terms of the Onsager relations for the (linear) conductance [20 -23]. A generic SO-Hamiltonian H involves products of velocity and spin operators that are invariant under time reversal. Even when spin-degenerate bands are split due to a broken inversion symmetry, the Kramers degeneracy remains intact. The Hamiltonian of the combined SOjF system has the symmetry TH m T ÿ1 H ÿm , where m is a unit vector in the direction of the magnetization of the FM and T the time-reversal operator. We n...

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Universal Intrinsic Spin Hall Effect

Cited by 2,126 publications

References 36 publications

Electric Octupole Order in Bilayer Ruthenate Sr₃Ru₂O₇

Electric Octupole Order in Bilayer Ruthenate Sr₃Ru₂O₇

Switching of perpendicular magnetization by spin–orbit torques in the absence of external magnetic fields

Detection of Current-Induced Spins by Ferromagnetic Contacts

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Universal Intrinsic Spin Hall Effect

Cited by 2,126 publications

References 36 publications

Electric Octupole Order in Bilayer Ruthenate Sr3Ru2O7

Electric Octupole Order in Bilayer Ruthenate Sr3Ru2O7

Switching of perpendicular magnetization by spin–orbit torques in the absence of external magnetic fields

Detection of Current-Induced Spins by Ferromagnetic Contacts

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Product

Resources

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Electric Octupole Order in Bilayer Ruthenate Sr₃Ru₂O₇

Electric Octupole Order in Bilayer Ruthenate Sr₃Ru₂O₇