Effective Reduction of Critical Current for Current-Induced Magnetization Switching by a Ru Layer Insertion in an Exchange-Biased Spin Valve

Jiang, Yi-Rong; Abe, Shinya; Ochiai, Tetsuyuki; Nozaki, Takayuki; Hirohata, Atsufumi; Tezuka, Nobuki; Inomata, K.

doi:10.1103/physrevlett.92.167204

Cited by 100 publications

(51 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spin torque changes sign for specific asymmetries giving rise to a new precessional state. After submission of this letter Jiang et al 24 reported a strongly reduced switching current by modifying the resistance distribution in the nanopillar by a Ru insertion.…”

Section: ͑5͒mentioning

confidence: 99%

Reducing the critical switching current in nanoscale spin valves

Manschot

Brataas

Bauer

2004

Applied Physics Letters

View full text Add to dashboard Cite

The current induced magnetization reversal in nanoscale spin valves is a potential alternative to magnetic field switching in magnetic memories. We show that the critical switching current can be decreased by an order of magnitude by strategically distributing the resistances in the magnetically active region of the spin valve. In addition, we simulate full switching curves and predict a new The prediction that a spin-polarized current can excite and reverse a magnetization 1,2 has been amply confirmed by recent experiments. 3,4 The current-induced magnetization dynamics is interesting as an efficient mechanism to write information into magnetic random access memories as well as to generate microwaves. 5 Unfortunately, the critical currents for magnetization reversal are still unattractively high. 6 In this letter, we apply a previously developed microscopic formalism 7 to understand the critical current in spin valves quantitatively and propose a strategy to reduce it by up to an order of magnitude. We also solve the micromagnetic equations with accurate angle-dependent magnetization torque and spin-pumping 8 terms and predict switching to a precessional state.We will first consider a generic F͑erromagnetic͉͒N͑ormal͉͒F spin valve biased by a voltage difference V. The two ferromagnetic reservoirs are assumed to be monodomain; the magnetizations differ by an angle . Charge and spin currents excited by an applied bias can be calculated accurately by magneto-electronic circuit theory 7 with parameters determined from first-principle calculations 9 that agree well with experimental data. 10 To this end we dissect the pillar into three nodes (the reservoirs and the normal metal) connected by two, not necessarily identical resistive elements G L and G R . Each of them is characterized by the conductance g = g ↑↑ + g ↓↓ , the polarization p = ͑g ↑↑ − g ↓↓ ͒ / g and the normalized mixing conductance =2g ↑↓ / g. g ↑↑ and g ↓↓ are, respectively, the conductances for electrons with spin parallel and antiparallel to the magnetization and g ↑↓ is the material parameter that governs the magnetization torque. The magnetically active region includes layers of thickness up to the spin-flip diffusion lengths from the interfaces. Any resistance outside this region is parasitic and not considered here. The conductances are effective parameters determined by the resistance of the ferromagnetic and normal metal bulk, that of the interfaces to the normal metal and the resistance of an eventual outer normal metal that fits into the magnetically active region. For simplicity we disregard the bulk resistance of the normal metal island and the imaginary part of g ↑↓ (for metallic interfaces smaller than 10% of the real part 9,11 ).The transverse component of the spin current is absorbed in the ferromagnet 11 and the associated spin-transfer torque can excite the magnetization. 1,2 Circuit theory has been used to derive analytic expressions for the torques in a symmetrical spin valve as function of the angle between the magnetization direc...

show abstract

Section: ͑5͒mentioning

confidence: 99%

Reducing the critical switching current in nanoscale spin valves

Manschot

Brataas

Bauer

2004

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…[3][4][5][6] There have been numerous studies which demonstrate the basic principle of STT switching and spin wave excitation. [5][6][7][8][9][10][11][12][13][14][15] Until recently, spin-wave excitation required the application of large fields (~1 T) to destabilise the AP state of the device, but recently zero-field spin-wave excitation has been reported in devices in which the spin-transfer torque can destabilise both the parallel and antiparallel alignment of the ferromagnetic layers. 16 This Letter reports similar behavior in devices for which the necessary spin-scattering asymmetry is enhanced by the use of an exchange bias layer coupled to a thin fixed layer rather than by making the free and fixed layers from different materials.…”

mentioning

confidence: 99%

Spin transfer switching and low-field precession in exchange-biased spin valve nanopillars

Aziz

Morecroft

et al. 2008

Applied Physics Letters

View full text Add to dashboard Cite

Using a three-dimensional focused-ion beam lithography process we have fabricated nanopillar devices which show spin transfer torque switching at zero external magnetic fields. Under a small in-plane external bias field, a field-dependent peak in the differential resistance versus current is observed similar to that reported in asymmetrical nanopillar devices. This is interpreted as evidence for the low-field excitation of spin waves which in our case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange bias layer coupled to a relatively thin CoFe fixed layer.

show abstract

“…The generated pure spin current enables the magnetization reversal of a nanomagnet with the same efficiency as in the case of using charge currents. These results are important for further theoretical developments in multiterminal structures 2 , but also with a view towards realizing novel devices driven by pure spin currents.In a vertical spin-valve nanopillar consisting of a ferromagnet/non-magnet/ferromagnet trilayer, the magnetic state can be switched between the antiparallel and the parallel configurations by applying a charge current [1][2][3][4][5][6][7][8][9][10][11] . This charge-current-induced magnetization switching (CIMS) is the result of a direct transfer of spin angular momentum from the spin current carried along the charge current to the localized magnetic moment in the ferromagnet.…”

mentioning

confidence: 99%

“…A spin current may interact with a magnetic nanostructure and give rise to spin-dependent transport phenomena, or excite magnetization dynamics [1][2][3][4][5][6][7][8][9][10][11] . In contrast to a spin-polarized charge current, a pure spin current does not produce any charge-related spurious effects 12,13 .…”

mentioning

confidence: 99%

Giant spin-accumulation signal and pure spin-current-induced reversible magnetization switching

2008

View full text Add to dashboard Cite

A number of proposed next-generation electronic devices, including novel memory elements 1 and versatile transistor circuits 2 , rely on spin currents, that is, the flow of electron angular momentum. A spin current may interact with a magnetic nanostructure and give rise to spin-dependent transport phenomena, or excite magnetization dynamics 1-11 . In contrast to a spin-polarized charge current, a pure spin current does not produce any charge-related spurious effects 12,13 . One way to produce a pure spin current is non-local electrical-spin injection 12-18 , but this approach has suffered so far from low injection efficiency. Here, we demonstrate a significant enhancement of the non-local injection efficiency in a lateral spin valve prepared with an entirely in situ fabrication process. Improvements to the interface quality and the device structure lead to an increase of the spin-signal amplitude by an order of magnitude. The generated pure spin current enables the magnetization reversal of a nanomagnet with the same efficiency as in the case of using charge currents. These results are important for further theoretical developments in multiterminal structures 2 , but also with a view towards realizing novel devices driven by pure spin currents.In a vertical spin-valve nanopillar consisting of a ferromagnet/non-magnet/ferromagnet trilayer, the magnetic state can be switched between the antiparallel and the parallel configurations by applying a charge current [1][2][3][4][5][6][7][8][9][10][11] . This charge-current-induced magnetization switching (CIMS) is the result of a direct transfer of spin angular momentum from the spin current carried along the charge current to the localized magnetic moment in the ferromagnet. Separation of the charge and spin components raises the possibility of chargeless pure spin-current-induced magnetization switching (pure spin CIMS).The pure spin current transfers only spin angular momentum, and thus provides an attractive means to manipulate the magnetic state in magnetic nanostructures as well as a quiet electrical background for experimental studies. The pure spin current I S can be generated by the diffusion of the accumulated spins 12-20 in a metallic lateral spin-valve (LSV) structure with non-local electrical spin injection, as shown in Fig. 1a. When the spin accumulation at the interface between the permalloy (Py) and Cu wires on the detector side is non-collinear to the Py magnetization, the transverse component of the pure spin CuAu Py

show abstract

Effective Reduction of Critical Current for Current-Induced Magnetization Switching by a Ru Layer Insertion in an Exchange-Biased Spin Valve

Cited by 100 publications

References 16 publications

Reducing the critical switching current in nanoscale spin valves

Reducing the critical switching current in nanoscale spin valves

Spin transfer switching and low-field precession in exchange-biased spin valve nanopillars

Giant spin-accumulation signal and pure spin-current-induced reversible magnetization switching

Contact Info

Product

Resources

About