Néel “orange-peel” coupling in magnetic tunneling junction devices

Schrag, B. D.; Anguelouch, A.; Ingvarsson, Snorri; Xiao, Gang; Long, Yu; Trouilloud, P. L.; Gupta, A.; Wanner, R.; Gallagher, W. J.; Parkin, S. S. P.

doi:10.1063/1.1315633

Cited by 151 publications

(89 citation statements)

References 10 publications

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“…6 The latter effect is of special importance in the context of giant magnetoresistance and tunnel magnetoresistance multilayer structures. [7][8][9][10] In Néel's orange-peel model, the effect of surface roughness is that of creating a surface magnetic charge distribution that contributes an extra term to the magnetic energy. This additional magnetostatic energy term leads to a reduction in the perpendicular uniaxial surface magnetic anisotropy, [11][12][13] but otherwise is isotropic in the plane of the film.…”

Section: Introductionmentioning

confidence: 99%

Effect of substrate roughness on the magnetic properties of thin fcc Co films

et al. 2007

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We present a study of the influence of substrate roughness on the magnetic properties of thin fcc Co films ͑7 and 17 nm thick͒ grown on Cu͑001͒/Si͑001͒. A significant decrease in cubic anisotropy with increasing film roughness was observed with Brillouin light scattering and magneto-optical Kerr effect magnetometry. In addition, the rougher samples showed a substantial broadening of the spin wave peaks. Both effects were found to be more pronounced for the thinner Co layers. Our observations are discussed in the framework of a theoretical model which takes into account the morphology of the Co films as measured by atomic force microscopy. While roughness effects are usually discussed in the context of Néel's "orange-peel" model, we propose a qualitatively different effect in this work whereby the magnetization follows coherently the substrate morphology ͑"undulating" state͒ resulting in the absence of magnetic surface charges. This magnetic configuration gives rise to a reduction in the magnetic anisotropy of epitaxial thin films, which is in good qualitative agreement with the experimental observations.

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Section: Introductionmentioning

confidence: 99%

Effect of substrate roughness on the magnetic properties of thin fcc Co films

et al. 2007

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“…For rough interfaces the so-called Néel-or orange peel interlayer coupling has to be considered. 3,4 In 1962, Néel 3 pointed out that there should be ferromagnetic coupling between adjacent films due to magnetic dipoles at the interface induced by a correlated morphological corrugation. Finally, if one considers the domain structure within each layer, a magnetostatic interaction could arise between the domain-wall stray fields in a FM / N / FM structure, where N can be a nonmagnetic metallic or insulating layer.…”

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confidence: 99%

Modulated magnetization depth profile in dipolarly coupled magnetic multilayers

et al. 2006

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Polarized neutron reflectivity ͑PNR͒ and magnetometry studies have been performed on the metal-insulator multilayer ͓Co 80 Fe 20 ͑1.6 nm͒ /Al 2 O 3 ͑3 nm͔͒ 9 which exhibits dominant dipolar coupling between the ferromagnetic layers. Our PNR measurements at the coercive field reveal a novel and unexpected magnetization state of the sample, exhibiting an oscillating magnetization depth profile from CoFe layer to CoFe layer with a period of five bilayers along the multilayer stack. With the help of micromagnetic simulations we demonstrate that competition between long-and short-ranged dipolar interactions apparently gives rise to this unprecedented phenomenon. DOI: 10.1103/PhysRevB.74.054426 PACS number͑s͒: 75.60.Jk, 61.12.Ha, 73.21.Ac, 78.20.Ls Magnetic multilayers ͑MLs͒ consisting of ferromagnetic ͑FM͒ and nonmagnetic ͑N͒ layers exhibit a large variety of physically interesting properties for both practical applications and fundamental research. In particular, magnetic multilayers comprising 3d ferromagnetic layers interleaved with nonmagnetic spacers exhibit giant magnetoresistance for appropriate thicknesses of the spacer layers.1 Several types of interlayer coupling have been studied theoretically and experimentally ͑e.g., Ref. 2͒. For trilayers consisting of two magnetically saturated, pinhole-free metallic layers separated by a conductive spacer layer, the Ruderman-Kittel-KasuyaYosida ͑RKKY͒ oscillatory exchange provides a major coupling mechanism. In systems with insulating spacer layers and flat interfaces, dipolar interactions are dominant. It favors antiparallel orientation of the intraplanar magnetization between adjacent layers. For rough interfaces the so-called Néel-or orange peel interlayer coupling has to be considered. 3,4 In 1962, Néel 3 pointed out that there should be ferromagnetic coupling between adjacent films due to magnetic dipoles at the interface induced by a correlated morphological corrugation. Finally, if one considers the domain structure within each layer, a magnetostatic interaction could arise between the domain-wall stray fields in a FM / N / FM structure, where N can be a nonmagnetic metallic or insulating layer. Recently Lew et al. 5 have shown that interlayer domain-wall coupling can induce a mirror domain structure in a magnetic trilayer system which can affect the transport properties.In this paper, we report on the observation of a novel magnetization state in a dipolar coupled magnetic metalinsulator multilayer exhibiting an oscillating magnetization depth profile from FM layer to FM layer. The paper is organized as follows: First we argue qualitatively how such unusual magnetization states can be induced by competing dipolar interactions. Then we present the experimental evidence from polarized neutron reflectometry. And, finally, a micromagnetic simulation is presented which underpins the argument that competing interactions can lead to the observed oscillating magnetization depth profile.Dipolar interaction can lead to frustration effects in magnetic multilayers wit...

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“…In Supplemental Material, we provide the reduced model for the more general case, where the bottom and top profiles of the film are different [33] (for a rigorous mathematical derivation, see [34]). Moreover, an analogous homogenization technique may be used to treat two coupled magnetic films with periodically modulated surfaces [35,36]; this problem will be treated elsewhere [37].…”

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Engineering Curvature-Induced Anisotropy in Thin Ferromagnetic Films

et al. 2017

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We investigate the effect of large curvature and dipolar energy in thin ferromagnetic films with periodically modulated top and bottom surfaces on magnetization behavior. We predict that the dipolar interaction and surface curvature can produce perpendicular anisotropy which can be controlled by engineering special types of periodic surface structures. Similar effects can be achieved by a significant surface roughness in the film. We demonstrate that, in general, the anisotropy can point in an arbitrary direction depending on the surface curvature. Furthermore, we provide simple examples of these periodic surface structures to show how to engineer particular anisotropies in thin films.

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Néel “orange-peel” coupling in magnetic tunneling junction devices

Cited by 151 publications

References 10 publications

Effect of substrate roughness on the magnetic properties of thin fcc Co films

Effect of substrate roughness on the magnetic properties of thin fcc Co films

Modulated magnetization depth profile in dipolarly coupled magnetic multilayers

Engineering Curvature-Induced Anisotropy in Thin Ferromagnetic Films

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