Ferromagnetic-resonance study of ultrathin bcc Fe(100) films grown epitaxially on fcc Ag(100) substrates

Heinrich, B.; Urquhart, K. B.; Arrott, A. S.; Cochran, J. F.; Myrtle, K.; Purcell, S. T.

doi:10.1103/physrevlett.59.1756

Cited by 291 publications

(86 citation statements)

References 9 publications

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“…Earlier experiments reported in Ref. [13] can also be understood by our model [14].We consider a ferromagnetic film sandwiched between two paramagnetic layers as shown in Fig. 1.…”

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confidence: 52%

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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“…Earlier experiments reported in Ref. [13] can also be understood by our model [14].We consider a ferromagnetic film sandwiched between two paramagnetic layers as shown in Fig. 1.…”

mentioning

confidence: 52%

Enhanced Gilbert Damping in Thin Ferromagnetic Films

2002

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“…6 Heinrich et al 14 observed an enhanced damping of Շ20-Å-thick Fe films when they were grown on Ag bulk substrates but no significant change in the damping constant was seen for films grown on GaAs even when the film thickness was reduced down to several atomic monolayers. 18 We will demonstrate here that our theory explains all these experimental findings well.…”

Section: 39-12mentioning

confidence: 99%

Spin pumping and magnetization dynamics in metallic multilayers

2002

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We study the magnetization dynamics in thin ferromagnetic films and small ferromagnetic particles in contact with paramagnetic conductors. A moving magnetization vector causes ''pumping'' of spins into adjacent nonmagnetic layers. This spin transfer affects the magnetization dynamics similar to the Landau-LifshitzGilbert phenomenology. The additional Gilbert damping is significant for small ferromagnets, when the nonmagnetic layers efficiently relax the injected spins, but the effect is reduced when a spin accumulation build-up in the normal metal opposes the spin pumping. The damping enhancement is governed by ͑and, in turn, can be used to measure͒ the mixing conductance or spin-torque parameter of the ferromagnet-normal-metal interface. Our theoretical findings are confirmed by agreement with recent experiments in a variety of multilayer systems.

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“…Several experiments [16][17][18][19][20] have shown that the orientation of the magnetic moment for thin Fe films (1 to 7 monolayers) is perpendicular to the film plane. In this case, due to the fact that the cross-product of the polarization vectors in the scattering configuration is in-plane, the occurrence of perpendicular magnetic moments is only reflected in the asymmetry ratio through interference with the scattering from in-plane moments.…”

Section: Resultsmentioning

confidence: 99%

X-ray resonant exchange scattering from 3d transition metal surfaces

Poppe

Fasolino

1995

Surface Science

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The decay of the elastic X-ray intensity peak versus perpendicular transferred momentum is theoretically studied at energies close to the LII edge, for single crystal Fe surfaces and thin Fe films. For the single crystal surface, large intensity changes are observed upon reversal of the direction of the magnetisation. For thin Fe films, which are known to exhibit perpendicular magnetisation, analogous effects are predicted when, by raising the temperature, the magnetisation becomes in-plane. These changes are sensitive to both direction and magnitude of the surface magnetic moments, making this technique a powerful probe for studying the magnetic properties of 3d surfaces and interfaces.

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Ferromagnetic-resonance study of ultrathin bcc Fe(100) films grown epitaxially on fcc Ag(100) substrates

Cited by 291 publications

References 9 publications

Enhanced Gilbert Damping in Thin Ferromagnetic Films

Enhanced Gilbert Damping in Thin Ferromagnetic Films

Spin pumping and magnetization dynamics in metallic multilayers

X-ray resonant exchange scattering from 3d transition metal surfaces

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