Ferromagnetic resonance study of sputtered Co|Ni multilayers

Beaujour, J-M. L.; Chen, W.; Krycka, Kathryn; Kao, C. C.; Sun, J. Z.; Kent, Andrew D.

doi:10.1140/epjb/e2007-00071-1

Cited by 88 publications

(74 citation statements)

References 35 publications

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“…Note that, for our Co/Ni system, we can simplify the v J expression [19]. Indeed, the damping parameter was measured to α ≈ 0.02 by ferromagnetic resonance (see also reference [31]) which leads to µ 0 H w ≈ 1.5 mT. Thus, in the precessional flow regime, we have α²<<1 and H w <<H, so that v J in Eq.…”

Section: The Combined Effect Of Magnetic Field and Current On Domain mentioning

confidence: 95%

Effect of spin transfer torque on domain wall motion regimes in [Co/Ni] superlattice wires

et al. 2017

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Section: The Combined Effect Of Magnetic Field and Current On Domain mentioning

confidence: 95%

Effect of spin transfer torque on domain wall motion regimes in [Co/Ni] superlattice wires

et al. 2017

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“…The transmitted signals are recorded while sweeping the magnetic field at constant microwave frequency f. (See Ref. [32] for more details on our FMR methods.) Here, we show results for two samples corresponding to the electrodes used in Fig.…”

Section: Ferromagnetic Resonance Spectroscopymentioning

confidence: 99%

Magnetic Fringe-Field Control of Electronic Transport in an Organic Film

et al. 2012

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Random, spatially uncorrelated nuclear-hyperfine fields in organic materials dramatically affect electronic transport properties such as electrical conductivity, photoconductivity, and electroluminescence. The influence of these nuclear-hyperfine fields can be overwhelmed by a uniform externally applied magnetic field, even at room temperature where the thermodynamic influences of the resulting nuclear and electronic Zeeman splittings are negligible. As a result, even in applied magnetic fields as small as 10 mT, the kinetics of exciton formation, bipolaron formation, and single-carrier hopping are all modified at room temperature, leading to changes in transport properties in excess of 10% in many materials. Here, we demonstrate a new method of controlling the electrical conductivity of an organic film at room temperature, using the spatially varying magnetic fringe fields of a magnetically unsaturated ferromagnet. (The fringe field is the magnetic field emanating from a ferromagnet, associated with magnetic dipole interactions or, equivalently, the divergence of the magnetization within and at the surfaces of the ferromagnet.) The ferromagnet's fringe fields might act as a substitute for either the applied magnetic field or the inhomogeneous hyperfine field. The size of the effect, the magnetic-field dependence, and hysteretic properties rule out a model where the fringe fields from the ferromagnet provide a local magnetic field that changes the electronic transport properties through the hyperfine field, and show that our effects originate from electrical transport through the inhomogeneous fringe fields coming from the ferromagnet. Surprisingly, these inhomogeneous fringe fields vary over length scales roughly 2 orders of magnitude larger than the hopping length in the organic materials, challenging the fundamental models of magnetoresistance in organic layers which require the correlation length of the inhomogeneous field to correspond roughly to the hopping length.

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“…We also measured resonance lines on an extended film with the same Co/Ni synthetic layer stack sandwiched between 10 nm Cu on each side. These measurements were conducted with a traditional rf field driven FMR using a flip-chip method [14]. Broader resonance peaks were not found in extended films with t =0.1, 0.2, and 0.3.…”

mentioning

confidence: 99%

Spin-torque driven ferromagnetic resonance of Co∕Ni synthetic layers in spin valves

Chen

Beaujour

Loubens

et al. 2008

Applied Physics Letters

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Spin-torque driven ferromagnetic resonance (ST-FMR) is used to study thin Co/Ni synthetic layers with perpendicular anisotropy confined in spin-valve based nanojunctions. Field swept ST-FMR measurements were conducted with a magnetic field applied perpendicular to the layer surface. The resonance lines were measured under low amplitude rf excitation, from 1 to 20 GHz. These results are compared with those obtained using conventional rf field driven FMR on extended films with the same Co/Ni layer structure. The layers confined in spin valves have a lower resonance field, a narrower resonance linewidth and approximately the same linewidth vs frequency slope, implying the same damping parameter. The critical current for magnetic excitations is determined from measurements of the resonance linewidth vs dc current and is in accord with the one determined from I-V measurements.Spin-transfer torque has been theoretically predicted and experimentally demonstrated to drive magnetic excitations in nanostructured spin valves and magnetic tunnel junctions [1,2,3,4,5]. With an rf current, spin transfer can be used to study ferromagnetic resonance [6,7]. This technique, known as spin-torque driven ferromagnetic resonance (ST-FMR), enables quantitative studies of the magnetic properties of thin layers in a spin-transfer device. Specifically, the layer magnetic anisotropy and damping can be determined [8], which are important parameters that need to be optimized in spin-torque-based memory and rf oscillator applications.Spin-transfer memory devices will likely include magnetic layers with perpendicular magnetic anisotropy that counteracts their shape-induced easy-plane anisotropy. This will allow efficient use of spin current for magnetic reversal with a reduced switching threshold [9] and a faster switching process [10]. Recent work by Mangin et al. [11] has demonstrated improvements of spin-torque efficiency in a spin valve that has perpendicularly magnetized Co/Ni synthetic layers. For further optimization of perpendicular anisotropy materials, it is important to have quantitative measurements of their anisotropy field and damping in a nanostructured device, as both of these parameters directly affect the threshold current for spintransfer induced switching.In this Letter, we present ST-FMR studies of bilayer nanopillars, where the thin (free) layer is composed of a Co/Ni synthetic layer and the thick (fixed) layer is pure Co. The magnetic anisotropy and damping of the Co/Ni have been determined by ST-FMR. We compare these results with those obtained from extended films with the same Co/Ni layer stack measured using traditional rf field driven FMR.Pillar junctions with submicron lateral dimensions ( Fig. 1(a)) were patterned on a silicon wafer using a nanostencil process [12]. Junctions were deposited using metal evaporation with the layer structure 1.5 nm (a)

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Ferromagnetic resonance study of sputtered Co|Ni multilayers

Cited by 88 publications

References 35 publications

Effect of spin transfer torque on domain wall motion regimes in [Co/Ni] superlattice wires

Effect of spin transfer torque on domain wall motion regimes in [Co/Ni] superlattice wires

Magnetic Fringe-Field Control of Electronic Transport in an Organic Film

Spin-torque driven ferromagnetic resonance of Co∕Ni synthetic layers in spin valves

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