Temperature variation of ferromagnetic relaxation in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>3</mml:mn><mml:mi /><mml:mi>d</mml:mi></mml:math>transition metals

Bhagat, S. M.; Lubitz, P.

doi:10.1103/physrevb.10.179

Cited by 236 publications

(131 citation statements)

References 19 publications

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“…We investigate the impact of soft layer damping variation in this work. For example, damping in Fe has been experimentally measured 13 to be 0.0018, which agrees well with its theoretical prediction 14 of 0.002. In contrast, damping in YIG has been measured 15 to be 0.0001.…”

Section: B Composite Free Layer Structuressupporting

confidence: 76%

Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

Bell

Victora

2017

AIP Advances

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We present a detailed numerical analysis of switching efficiency for the recently proposed dual referenced composite free layer structure with respect to Gilbert damping. Low anisotropy assistive layers enable reduction of Gilbert damping and an increase of partial spin polarization within those low anisotropy layers—not feasible with single layer structures that require high anisotropy for thermal stability. When the damping of the soft layers is ultra-low, an efficiency (kBT/μA) of 8.1 is achieved for the composite structure with perpendicular anisotropy. This represents an improvement of 286% and 913% relative to the state-of-the-art dual-referenced and conventional STT-RAM cells, respectively. Results for structures with longitudinal anisotropy are also presented. A linear calculation of the STT polarization pre-factor is also described that captures all reflections.

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Section: B Composite Free Layer Structuressupporting

confidence: 76%

Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

Bell

Victora

2017

AIP Advances

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“…2, bottom), characteristic of 5d impurities in the pure hosts Fe and Ni [18,19]. In spite of this behaviour of µ 5d spin the variation [20] of α(x) seems again to be correlated with the density of states n 5d (E F ) (Fig. 2 bottom).…”

Section: Introductionmentioning

confidence: 99%

Ab InitioCalculation of the Gilbert Damping Parameter via the Linear Response Formalism

et al. 2011

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A Kubo-Greenwood-like equation for the Gilbert damping parameter α is presented that is based on the linear response formalism. Its implementation using the fully relativistic Korringa-KohnRostoker (KKR) band structure method in combination with Coherent Potential Approximation (CPA) alloy theory allows it to be applied to a wide range of situations. This is demonstrated with results obtained for the bcc alloy system FexCo1−x as well as for a series of alloys of permalloy with 5d transition metals. To account for the thermal displacements of atoms as a scattering mechanism, an alloy-analogy model is introduced. The corresponding calculations for Ni correctly describe the rapid change of α when small amounts of substitutional Cu are introduced.

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“…The study of a in bulk metallic ferromagnets has drawn significant interest over several decades. Notwithstanding the large body of both experimental [2] and theoretical [3] work, the damping mechanism in bulk ferromagnets is not yet fully understood.…”

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confidence: 99%

Enhanced Gilbert Damping in Thin Ferromagnetic Films

2002

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The precession of the magnetization of a ferromagnet is shown to transfer spins into adjacent normal metal layers. This "pumping" of spins slows down the precession corresponding to an enhanced Gilbert damping constant in the Landau-Lifshitz equation. The damping is expressed in terms of the scattering matrix of the ferromagnetic layer, which is accessible to model and first-principles calculations. Our estimates for permalloy thin films explain the trends observed in recent experiments. DOI: 10.1103/PhysRevLett.88.117601 PACS numbers: 76.50. +g, 72.25.Mk, 73.40. -c, 75.75. +a The magnetization dynamics of a bulk ferromagnet is well described by the phenomenological Landau-Lifshitz-where m is the magnetization direction, g is the gyromagnetic ratio, and H eff is the effective magnetic field including the external, demagnetization, and crystal anisotropy fields. The second term on the right-hand side of Eq. (1) was first introduced by Gilbert [1] and the dimensionless coefficient a is called the Gilbert damping constant. For a constant H eff and a 0, m precesses around the field vector with frequency v gH eff . When damping is switched on a . 0, the precession spirals down to a time independent magnetization along the field direction on a time scale of 1͞av. The study of a in bulk metallic ferromagnets has drawn significant interest over several decades. Notwithstanding the large body of both experimental [2] and theoretical [3] work, the damping mechanism in bulk ferromagnets is not yet fully understood.The magnetization dynamics in thin magnetic films and microstructures is technologically relevant for, e.g., magnetic recording applications at high bit densities. Recent interest by the basic physics community in this topic is motivated by the spin-current induced magnetization switching in layered structures [4 -6]. The Gilbert damping constant was found to be 0.04 , a , 0.22 for Cu-Co and Pt-Co [5,7], which is considerably larger than the bulk value a 0 ഠ 0.005 in Co [6,8]. Previous attempts to explain the additional damping in magnetic multilayer systems involved an enhanced electron-magnon scattering near the interface [9] and other mechanisms [10], both in equilibrium and in the presence of a spin-polarized current.In this Letter we propose a novel mechanism for the Gilbert damping in normal-metal-ferromagnet ͑N-F͒ hybrids. According to Eq. (1), the precession of the magnetization direction m is caused by the torque~m 3 H eff . This is physically equivalent to a volume injection of what we call a "spin current." The damping occurs when the spin current is allowed to leak into a normal metal in contact with the ferromagnet. Our mechanism is thus the inverse of the spin-current induced magnetization switching: A spin current can exert a finite torque on the ferromagnetic order parameter, and, vice versa, a moving magnetization vector loses torque by emitting a spin current. In other words, the magnetization precession acts as a spin pump which transfers angular momentum from the ferromagnet into the norma...

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Temperature variation of ferromagnetic relaxation in the3dtransition metals

Cited by 236 publications

References 19 publications

Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

Ab InitioCalculation of the Gilbert Damping Parameter via the Linear Response Formalism

Enhanced Gilbert Damping in Thin Ferromagnetic Films

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