Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5–10 GHz frequency range

Bonetti, Stefano; Kukreja, Roopali; Zhao, Chen; Spoddig, D.; Ollefs, Katharina; Schöppner, Christian; Meckenstock, R.; Ney, Andreas; Pinto, Jude; Houanche, Richard; Frisch, J.; Stöhr, J.; Dürr, H. A.; Ohldag, Hendrik

doi:10.1063/1.4930007

Cited by 49 publications

(55 citation statements)

References 27 publications

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“…This recently reported STXM-FMR technique enables direct time-dependent imaging of the spatial distribution of the precessing magnetization over the sample during FMR excitation. [26][27][28][29] In most of the cases, spin-waves are investigated using a nonuniform excitation of the structure. 2,4,10,12 When the uniform excitation field is applied to the specimen, it is also possible to excite spin-waves, but only standing spin-waves are expected.…”

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confidence: 99%

“…2(a). 26,27 The transmitted light intensity depends on the relative directions of the x-rays' polarization and dynamic component of the magnetization, the so-called x-ray magnetic circular dichroism (XMCD) effect. Thus, the maximum and minimum intensities on the STXM-FMR images (white and black contrast in the scans) mean the maximum deviation of the dynamic component of the magnetisation in opposite directions.…”

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confidence: 99%

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Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation

Pile

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Schaffers

et al. 2020

Applied Physics Letters

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A non-standing character of directly imaged spin-waves in confined micron-sized ultrathin permalloy (Ni 80 Fe 20 ) structures is reported along with evidence of the possibility to alter the observed state by modifications to the sample geometry. Using micromagnetic simulations the presence of the spin-wave modes excited in the permalloy stripes along with the quasi-uniform modes were calculated. The predicted spin-waves were imaged in direct space using time resolved scanning transmission X-ray microscopy, combined with a ferromagnetic resonance excitation scheme (STXM-FMR). STXM-FMR measurements revealed a non-standing character of the spin-waves. Also it was shown by micromagnetic simulations and confirmed with STXM-FMR results that the observed character of the spin-waves can be influenced by the local magnetic fields in different sample geometries.

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confidence: 99%

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Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation

Pile

Feggeler

Schaffers

et al. 2020

Applied Physics Letters

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“…It directly probes the spin polarization of the valence electronic states via x-ray induced excitation of core level electrons. Small changes of the magnetization of 10 −4 or less can be recorded with a spatial resolution of about 35 nm using state of the art x-ray optics in combination with a synchrotron as a tunable, polarized, and pulsed soft x-ray source [14,15].…”

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Direct Observation of a Localized Magnetic Soliton in a Spin-Transfer Nanocontact

et al. 2015

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We report the direct observation of large amplitude spin-excitations localized in a spin-transfer nanocontact using scanning transmission x-ray microscopy. Experiments were conducted using a nanocontact to an ultrathin ferromagnetic multilayer with perpendicular magnetic anisotropy. Element resolved x-ray magnetic circular dichroism images show an abrupt onset of spin excitations at a threshold current that are localized beneath the nanocontact, with average spin precession cone angles of 25 • at the contact center. The results strongly suggest that we have observed a localized magnetic soliton.

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“…Only very recently has it been possible to perform time-resolved XMCD experiments with the combined temporal and spatial resolution needed to record a "movie" of the spin wave dynamics at the nanoscale in an in-plane magnetised nanocontact [110]. One of the technical steps that had to be implemented was to extend the capabilities of the time-resolved XMCD up to the ∼ 10 GHz rate [46].…”

Section: Spin Waves In Spin Torque Oscillatorsmentioning

confidence: 99%

X-ray imaging of spin currents and magnetisation dynamics at the nanoscale

Bonetti

2017

J. Phys.: Condens. Matter

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Abstract. Understanding how spins move in time and space is the aim of both fundamental and applied research in modern magnetism. Over the past three decades, research in this field has led to technological advances that have had a major impact on our society, while improving the understanding of the fundamentals of spin physics. However, important questions still remain unanswered, because it is experimentally challenging to directly observe spins and their motion with a combined high spatial and temporal resolution. In this article, we present an overview of the recent advances in X-ray microscopy that allow researchers to directly watch spins move in time and space at the microscopically relevant scales. We discuss scanning X-ray transmission microscopy (STXM) at resonant soft X-ray edges, which is available at most modern synchrotron light sources. This technique measures magnetic contrast through the X-ray magnetic circular dichroism (XMCD) effect at the resonant absorption edges, while focusing the X-ray radiation at the nanometre scale, and using the intrinsic pulsed structure of synchrotron-generated X-rays to create time-resolved images of magnetism at the nanoscale. In particular, we discuss how the presence of spin currents can be detected by imaging spin accumulation, and how the magnetisation dynamics in thin ferromagnetic films can be directly imaged. We discuss how a direct look at the phenomena allows for a deeper understanding of the the physics at play, that is not accessible to other, more indirect techniques. Finally, we present an overview of the exciting opportunities that lie ahead to further understand the fundamentals of novel spin physics, opportunities offered by the appearance of diffraction limited storage rings and free electron lasers.

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Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5–10 GHz frequency range

Cited by 49 publications

References 27 publications

Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation

Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation

Direct Observation of a Localized Magnetic Soliton in a Spin-Transfer Nanocontact

X-ray imaging of spin currents and magnetisation dynamics at the nanoscale

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