Spin-Polarized Electron Energy Loss Spectroscopy of High Energy, Large Wave Vector Spin Waves in Ultrathin fcc Co Films on Cu(001)

Vollmer, R.; Etzkorn, Markus; Kumar, P. S. Anil; Ibach, H.; Kirschner, J.

doi:10.1103/physrevlett.91.147201

Cited by 168 publications

(108 citation statements)

References 21 publications

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“…Spin-polarized high-resolution electron energy loss spectroscopy (SPEELS) was used to study the magnetic excitations. Due to its monolayer sensitivity, possibility of measuring magnetic excitations over the whole surface Brillouin zone and the capability of investigating spin-dependent scattering, SPEELS is a powerful technique for probing terahertz magnons in ultrathin ferromagnetic films [22][23][24][25][26][27][28][29][30] . A schematic representation of the scattering geometry in our SPEELS experiments is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Long-living terahertz magnons in ultrathin metallic ferromagnets

et al. 2015

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The main idea behind magnonics is to use the elementary magnetic excitations (magnons) for information transfer and processing. One of the main challenges, hindering the application of ultrafast terahertz magnons in magnonics, has been the short lifetime of these excitations in metallic ferromagnets. Here, we demonstrate that the engineering of the electronic structure of a ferromagnetic metal, by reducing its dimensionality and changing its chemical composition, opens a possibility to strongly suppress the relaxation channels of terahertz magnons and thereby enhance the magnons' lifetime. For the first time, we report on the long-lived terahertz magnons excited in ultrathin metallic alloy films. On the basis of the first-principles calculations, we explain the microscopic nature of the long lifetime being a consequence of the peculiar electronic hybridizations of the species. We further demonstrate a way of tailoring magnon energies (frequencies) by varying the chemical composition of the film.

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Section: Resultsmentioning

confidence: 99%

Long-living terahertz magnons in ultrathin metallic ferromagnets

et al. 2015

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“…Many studies are focusing on the dynamical magnetic properties (e.g., spinwaves), as key properties such as the time it takes to switch a magnetic bit or to transport magnetic information are dynamical processes. A technique that is very suitable to study spin-waves in thin films is electronenergy-loss spectroscopy (EELS) or its spin-polarized version (SPEELS) [9][10][11][12][13] . Electrons have a much larger scattering cross section than neutrons (routinely used to probe spin-waves in bulk materials), which compensates for the much smaller scattering volume of a thin magnetic film.…”

Section: Introductionmentioning

confidence: 99%

“…The study of spin-waves at surfaces and thin films by EELS was already proposed back in 1967 by Mills 10 . However, it took more than three decades until specialized electron spectrometers were built, allowing the first investigations 12,13 . Originally only one spin-wave mode was experimentally observed 13 .…”

Section: Introductionmentioning

confidence: 99%

First-principles investigation of spin-wave dispersions in surface-reconstructed Co thin films on W(110)

2017

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We computed spin-wave dispersions of surface-reconstructed Co films on the W(110) surface in the adiabatic approximation. The magnetic exchange interactions are obtained via first-principles electronic-structure calculations using the Korringa-Kohn-Rostoker Green-function method. We analyze the strength and oscillatory behavior of the intralayer and interlayer magnetic interactions and investigate the resulting spin-wave dispersions as a function of the thickness of Co films. In particular, we highlight and explain the strong impact of hybridization of the electronic states at the Co-W interface on the magnetic exchange interactions and on the spin-wave dispersions. We compare our results to recent measurements based on electron-energy-loss spectroscopy [E. Michel, H. Ibach, and C.M. Schneider, Phys. Rev. B 92, 024407 (2015)]. Good overall agreement with experimental findings can be obtained by considering the possible overestimation of the spin splitting, stemming from the local-spin-density approximation, and adopting an appropriate correction.

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“…Indeed, spin waves up to the Brillouin-zone boundary are observed in Fe and Co, which have substantially larger exchange splittings than Ni. [89][90][91][92] On the theoretical side, the first attempt to use realistic energy bands for Ni in the calculations of a generalized susceptibility was undertaken by Lowde and Windsor. 84 The authors calculated the magnetic susceptibility within the RPA for rigidly spin-split bands, but the agreement with the available experimental data was not good.…”

Section: B Collective Spin-wave Excitationsmentioning

confidence: 99%

Wannier-function approach to spin excitations in solids

et al. 2010

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We present a computational scheme to study spin excitations in magnetic materials from first principles. The central quantity is the transverse spin susceptibility, from which the complete excitation spectrum, including single-particle spin-flip Stoner excitations and collective spin-wave modes, can be obtained. The susceptibility is derived from many-body perturbation theory and includes dynamic correlation through a summation over ladder diagrams that describe the coupling of electrons and holes with opposite spins. In contrast to earlier studies, we do not use a model potential with adjustable parameters for the electron-hole interaction but employ the random-phase approximation. To reduce the numerical cost for the calculation of the four-point scattering matrix we perform a projection onto maximally localized Wannier functions, which allows us to truncate the matrix efficiently by exploiting the short spatial range of electronic correlation in the partially filled d or f orbitals. Our implementation is based on the full-potential linearized augmented-plane-wave method. Starting from a ground-state calculation within the local-spin-density approximation ͑LSDA͒, we first analyze the matrix elements of the screened Coulomb potential in the Wannier basis for the 3d transition-metal series. In particular, we discuss the differences between a constrained nonmagnetic and a proper spin-polarized treatment for the ferromagnets Fe, Co, and Ni. The spectrum of single-particle and collective spin excitations in fcc Ni is then studied in detail. The calculated spin-wave dispersion is in good overall agreement with experimental data and contains both an acoustic and an optical branch for intermediate wave vectors along the ͓1 0 0͔ direction. In addition, we find evidence for a similar double-peak structure in the spectral function along the ͓1 1 1͔ direction. To investigate the influence of static correlation we finally consider LSDA+ U as an alternative starting point and show that, together with an improved description of the Fermi surface, it yields a more accurate quantitative value for the spin-wave stiffness constant, which is overestimated in the LSDA.

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Spin-Polarized Electron Energy Loss Spectroscopy of High Energy, Large Wave Vector Spin Waves in Ultrathin fcc Co Films on Cu(001)

Cited by 168 publications

References 21 publications

Long-living terahertz magnons in ultrathin metallic ferromagnets

Long-living terahertz magnons in ultrathin metallic ferromagnets

First-principles investigation of spin-wave dispersions in surface-reconstructed Co thin films on W(110)

Wannier-function approach to spin excitations in solids

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