Current-perpendicular (CPP) magnetoresistance in magnetic metallic multilayers

Bass, J.; Pratt, W. P.

doi:10.1016/s0304-8853(99)00316-9

Cited by 372 publications

(295 citation statements)

References 98 publications

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“…[16] and [17] parameters mostly derived from CPP-GMR experimental data [22][23]. For respectively Au, Py, Cu, Co and Ta, these parameters are: bulk resistivity ρ (μΩ.cm) = 2, 15, 2.9, 24, 170; bulk spin asymmetry coefficient β = 0, 0.76, 0, 0.46, 0; spin diffusion length l sf (nm) = 35, 4, 350, 38, 10.…”

Section: Methodsmentioning

confidence: 99%

“…We present the results of calculations in the models of Fert et al [15] and Barnaś et al [16][17] for a Py(8)/Cu(10)/Co(8) pillar. With respect to standard structures like Co/Cu/Co or Py/Cu/Py, the difference we have introduced is a large asymmetry between the spin diffusion lengths (SDL) in the magnetic layers, with a long SDL in Co ≈ 38 nm (at room temperature) and a short SDL in Py ≈ 4 nm [22][23]. The smaller spin asymmetry of the resistivity in Co could also affect the angular dependence but we have checked by additional calculations that the wavy variation comes primarily from the shorter SDL in the Py free layer and not from the different spin asymmetry coefficients, as this has been mistakenly written in Ref.…”

mentioning

confidence: 99%

“…In addition, the observation of a wavy angular dependence of the torque represents a valuable test of the theory and shows that realistic predictions of the spin transfer torque and its angular dependence in a given structure are now possible. As we will see, in the models we consider here [15][16], the torque is calculated from parameters which, for most of them, can be derived from former CPP-GMR experiments [22][23]. The usual behaviour observed in pillars with in-plane magnetizations along an anisotropy axis corresponds to the standard angular dependence of the inset of Fig.1a, in which the torque starts from zero at ϕ = 0 (P equilibrium state with parallel magnetizations of the fixed and free magnetic layers) and keeps the same sign till it comes back to zero at ϕ = π (AP antiparallel state).…”

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confidence: 99%

“…Note that the measured emitted power is therefore only a fraction of the actual emitted power from the pillars. Both transport and frequency measurements have been performed at room temperature and with in-plane magnetic field.The torques of Fig.1a have been calculated by introducing in the models of Refs.[16] and [17] parameters mostly derived from CPP-GMR experimental data [22][23]. For respectively Au, Py, Cu, Co and Ta, these parameters are: bulk resistivity ρ (μΩ.cm) = 2, 15, 2.9, 24, 170; bulk spin asymmetry coefficient β = 0, 0.76, 0, 0.46, 0; spin diffusion length l sf (nm) = 35, 4, 350, 38, 10.…”

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Shaped angular dependence of the spin-transfer torque and microwave generation without magnetic field

et al. 2007

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The generation of oscillations in the microwave frequency range is one of the most important applications expected from spintronics devices exploiting the spin transfer phenomenon. We report transport and microwave power measurements on specially designed nanopillars for which a non-standard angular dependence of the spin transfer torque (wavy variation) is predicted by theoretical models. We observe a new kind of current-induced dynamics that is characterized by large angle precessions in the absence of any applied field, as this is also predicted by simulation with such a wavy angular dependence of the torque. This type of non-standard nanopillars can represent an interesting way for the implementation of spin transfer oscillators since they are able to generate microwave oscillations without applied magnetic field. We also emphasize the theoretical implications of our results on the angular dependence of the torque. 2The magnetization of a ferromagnetic body can be manipulated by transfer of spin angular momentum from a spin-polarized current. This is the concept of spin transfer introduced by Slonczewski [1] and Berger [2] in 1996. In most experiments, a spin-polarized current is injected from a spin polarizer into a "free" magnetic element, for example in pillar-shaped magnetic trilayers [3][4][5][6]. The phenomenon of spin transfer has a great potential for applications. It can be used either to switch a magnetic configuration (the configuration of a magnetic memory for example) [3][4][5] or to generate magnetic precessions and voltage oscillations in the microwave frequency range [6][7]. In the most usual situations, such oscillations are observed in the presence of a magnetic field.From a fundamental point of view, spin transfer effects raise two different types of problems [8]. First the spin transfer torque acting on a magnetic element is related to the transverse spin polarisation of the current (transverse meaning perpendicular to the magnetization axis of the element) and can be derived from spin-dependent transport equations [8][9][10][11][12][13][14][15][16][17]. On the other hand, the description of the magnetic excitations generated by the spin transfer torque raises problems of non-linear dynamics [8,[18][19][20]. For example, in the simple limit where the excitation is supposed to be a uniform precession of the magnetization (macrospin approximation), this precession can be determined by introducing the spin transfer torque into a Landau-LifshitzGilbert (LLG) equation for the motion of the magnetic moment. However, the determination of the spin transfer torque and the description of the magnetization dynamics cannot be regarded as independent problems. In standard trilayered structures with in-plane magnetizations and with the usual angular dependence, a switching regime is found at zero and low magnetic field and the precession regime with generation of voltage oscillations is mainly observed above some threshold field [8]. We will show that a new behavior, characterized by large a...

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Shaped angular dependence of the spin-transfer torque and microwave generation without magnetic field

et al. 2007

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“…One choice is AR F/N ↑ and AR F/N ↓, where ↑ and ↓ means that the magnetic moment of the currentcarrying-electron points along or opposite to the magnetization of the F-layer. A choice more convenient for use in the two-current series-resistor (2CSR) model [9][10][11] or the Valet-Fert generalization to finite spin-diffusion lengths, 10 To achieve a uniform measuring current through a spin-valve of macroscopic area A ~ 1.2 mm 2 , we sandwich it between crossed superconducting (S) Nb leads. Our sample geometry, preparation, and measuring techniques, are described in detail elsewhere.…”

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Changes in magnetic scattering anisotropy at a ferromagnetic/superconducting interface

2004

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We show that some metals and alloys (X = Cu, Ag, FeMn, or Cu and Ag combined with each other), sputtered between ferromagnetic Co and superconducting Nb, produce no change in current-perpendicular-to-plane magnetoresistance (CPP-MR) in a carefully designed CPP-spin-valve. In contrast, other metals (Ru or Au) or combinations (Cu or Ag combined with Au, Ru, or FeMn) change the CPP-MR, in some cases even reversing its sign. We ascribe these changes to activation of magnetic scattering anisotropies at a ferromagnetic/superconducting interface, apparently by strong spin-flipping between the Co and Nb layers.

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GMR in Granular CuFe with a Face Centered Tetragonal Structure of Iron

Ebert

Ghafari

Stahl

et al. 2002

phys. stat. sol. (a)

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Granular thin CuFe films with a face centered tetragonal (fct) structure of Fe clusters in Cu matrix show a giant magnetoresistance effect. The samples were prepared by co-deposition of 57 Fe and Cu metal in Ultra High Vacuum. The role of the scattering of conduction electrons at the interface between Fe ultrafine particles and Cu matrix has been studied by Mö ssbauer spectroscopy and magnetoresitivity measurements. The ratio of Fe atoms located at Cu/Fe interface and in the ultrafine particles (bulk) was resolved by Mö ssbauer spectroscopy. In the system consisting of ultrafine fct-Fe particles imbedded in Cu matrix the giant magnetoresistance effect is not correlated to the ratio of interface/bulk in contrast to observations in FeAg granular system. The spin-dependent scattering of conduction electrons occurs within the ferromagnetic fct-Fe particles.

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Current-perpendicular (CPP) magnetoresistance in magnetic metallic multilayers

Cited by 372 publications

References 98 publications

Shaped angular dependence of the spin-transfer torque and microwave generation without magnetic field

Shaped angular dependence of the spin-transfer torque and microwave generation without magnetic field

Changes in magnetic scattering anisotropy at a ferromagnetic/superconducting interface

GMR in Granular CuFe with a Face Centered Tetragonal Structure of Iron

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