Batch-fabricated spin-injection magnetic switches

Sun, J. Z.; Monsma, D. J.; Abraham, David W.; Rooks, M. J.; Koch, R. H.

doi:10.1063/1.1506794

Cited by 147 publications

(100 citation statements)

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“…Spin-transfer torque studies on pillar devices concentrated on magnetic fields applied in the thin film plane. In the low-field regime, a hysteretic jump in the differential resistance was observed; clear evidence for current induced magnetization reversal of one of the magnetic layers [8,9,10,11,12,13,14]. Hence, the effect of the spin-polarized current on the magnetization seemed to be quite distinct in the low and high field regime.…”

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confidence: 88%

“…Subsequent experiments have concentrated on the reduction of the lateral size of Co/Cu/Co trilayers to the sub-micron scale, resulting in the fabrication of nanopillar devices [8,9,10,11,12,13,14]. In the point contact experiments the applied magnetic field was oriented perpendicular to the thin film plane and was larger than the film demagnetization fields (H≥2 T).…”

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confidence: 99%

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Current-Induced Magnetization Reversal in High Magnetic Fields inCo/Cu/CoNanopillars

et al. 2003

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Current-induced magnetization dynamics in Co/Cu/Co trilayer nanopillars (∼100 nm in diameter) have been studied experimentally at low temperatures for large applied fields perpendicular to the layers. At 4.2 K an abrupt and hysteretic increase in resistance is observed at high current densities for one polarity of the current, comparable to the giant magnetoresistance (GMR) effect observed at low fields. A micromagnetic model, that includes a spin-transfer torque, suggests that the current induces a complete reversal of the thin Co layer to alignment antiparallel to the applied field-that is, to a state of maximum magnetic energy.

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confidence: 88%

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confidence: 99%

Current-Induced Magnetization Reversal in High Magnetic Fields inCo/Cu/CoNanopillars

et al. 2003

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“…2c and 2d, microwave signals can sometimes be observed not only at large H where dynamical modes have been postulated previously, 4,[6][7][8]12,[14][15][16] but also in the small-H regime of current-driven hysteretic switching. While sweeping to increasing currents at H = 500 Oe, for example, microwave peaks corresponding to small-angle precession exist for I within ~ 0.7 mA below the current for P to AP switching.…”

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confidence: 95%

Microwave oscillations of a nanomagnet driven by a spin-polarized current

Kiselev

Sankey

Krivorotov

et al. 2003

Nature

1,976

1,595

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† These authors contributed equally to this workThe recent discovery that a spin-polarized electrical current can apply a large torque to a ferromagnet, through direct transfer of spin angular momentum, offers the intriguing possibility of manipulating magnetic-device elements without applying cumbersome magnetic fields. 1-16 However, a central question remains unresolved:What type of magnetic motions can be generated by this torque? Theory predicts that spin transfer may be able to drive a nanomagnet into types of oscillatory magnetic modes not attainable with magnetic fields alone, 1-3 but existing measurement techniques have provided only indirect evidence for dynamical states. 4,6-8,12,14-16 The nature of the possible motions has not been determined. Here we demonstrate a technique that allows direct electrical measurements of microwave-frequency dynamics in individual nanomagnets, propelled by a DC spin-polarised current. We show that in fact spin transfer can produce several different types of magnetic excitations. Although there is no mechanical motion, a simple magnetic-multilayer structure acts like a nanoscale motor; it converts energy from a DC electrical current into high-frequency magnetic rotations that might be applied in new devices including microwave sources and resonators. 2 We examine samples made by sputtering a multilayer of 80 nm Cu / 40 nm Co / 10 nm Cu / 3 nm Co / 2 nm Cu / 30 nm Pt onto an oxidized silicon wafer and then milling through part of the multilayer (Fig. 1a) to form a pillar with an elliptical cross section of lithographic dimensions 130 nm ¥ 70 nm. 17 Top contact is made with a Cu electrode.Transmission or reflection of electrons from the thicker "fixed" Co layer produces a spinpolarised current that can apply a torque to the thinner "free" Co layer. Subsequent oscillations of the free-layer magnetization relative to the fixed layer change the device resistance 18 so, under conditions of DC current bias, magnetic dynamics produce a timevarying voltage (with typical frequencies in the microwave range). If the oscillations were exactly symmetric relative to the direction to the fixed-layer moment, voltage signals would occur only at multiples of twice the fundamental oscillation frequency, f. To produce signal strength at f, we apply static magnetic fields (H) in the sample plane a few degrees away from the magnetically-easy axis of the free layer. All data are taken at room temperature, and by convention positive current I denotes electron flow from the free to the fixed layer.In characterization measurements done at frequencies < 1 kHz, the samples exhibit the same spin-transfer-driven changes in resistance reported in previous experiments 7,9 (Fig. 1b). For H smaller than the coercive field of the free layer (H c ~ 600 Oe), an applied current produces hysteretic switching of the magnetic layers between the low-resistance parallel (P) and high-resistance antiparallel (AP) states. Sweeping H can also drive switching between the P and AP states (Fig 1b, inset). For H larger ...

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“…This mechanism of STT was initially proposed by Berger et al [8] and Slonczewski [9] in 1996 and attracted significant interests because of the great potential for direct current-induced spintronic devices [10][11][12]. The role of STT in magnetization switching has been verified by numerous experiments in spin-valve nanopillars [13][14][15], magnetic nanowires [16,17], point contact geometry [18][19][20], and magnetic tunnel junctions [21][22][23][24]. The most attractive application of currentinduced magnetization switching is magnetic random-access memory (MRAM), which has the advantages of nonvolatile, high addressing speed, low-energy consumption, and avoidance of cross writing.…”

Section: Introductionmentioning

confidence: 71%

Micromagnetic Simulation of Spin Transfer Torque Magnetization Precession Phase Diagram in a Spin-Valve Nanopillar under External Magnetic Fields

Huang

Liu

et al. 2012

ISRN Condensed Matter Physics

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We investigated spin transfer torque magnetization precession in a nanoscale pillar spin-valve under external magnetic fields using micromagnetic simulation. The phase diagram of the magnetization precession is calculated and categorized into four states according to their characteristics. Of the four states, the precessional state has two different modes: steady precession mode and substeady precession mode. The different modes originate from the dynamic balance between the spin transfer torque and the Gilbert damping torque. Furthermore, we reported the behavior of the temporal evolutions of magnetization components in steady precession mode at the condition of the applied magnetic field using the orbit projection method and explaining perfectly the magnetization components evolution behavior. In addition, a result of a nonuniform magnetization distribution is observed in the free layer due to the excitation of non-uniform mode.

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Batch-fabricated spin-injection magnetic switches

Abstract: A study of spin relaxation on spin transfer switching of a noncollinear magnetic multilayer structure J. Appl. Phys.

Cited by 147 publications

References 10 publications

Current-Induced Magnetization Reversal in High Magnetic Fields inCo/Cu/CoNanopillars

Current-Induced Magnetization Reversal in High Magnetic Fields inCo/Cu/CoNanopillars

Microwave oscillations of a nanomagnet driven by a spin-polarized current

Micromagnetic Simulation of Spin Transfer Torque Magnetization Precession Phase Diagram in a Spin-Valve Nanopillar under External Magnetic Fields

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