13 research outputs found
Direct visualization of dynamic magnetic coupling in a Co/Py bilayer with picosecond and nanometer resolution
We present a combination of ferromagnetic resonance (FMR) with spatially and
time-resolved X-ray absorption spectroscopy in a scanning transmission X-ray
microscope (STXM-FMR). The transverse high frequency component of the
resonantly excited magnetization is measured with element-specifity in a
Permalloy (Py) disk - Cobalt (Co) stripe bilayer microstructure. STXM-FMR
mappings are snapshots of the local magnetization-precession with nm spatial
resolution and ps temporal resolution. We directly observe the transfer of
angular momentum from Py to Co and vice versa at their respective
element-specific resonances. A third resonance could be observed in our
experiments, which is identified as a coupled resonance of Py and Co.Comment: Version submitted to Physical Review Applied with updated author list
and supplemental information (Ancillary file
Unidirectional anisotropy in cubic FeGe with antisymmetric spin-spin-coupling
We report strong unidirectional anisotropy in bulk polycrystalline B20 FeGe
measured by ferromagnetic resonance spectroscopy. Bulk and micron-sized samples
were produced and analytically characterized. FeGe is a B20 compound with
inherent Dzyaloshinskii-Moriya interaction. Lorenz microscopy confirms a
skyrmion lattice at in a magnetic field of 150 mT.
Ferromagnetic resonance was measured at ,
near the Curie temperature. Two resonance modes were observed, both exhibit a
unidirectional anisotropy of in
the primary, and in the secondary
mode, previously unknown in bulk ferromagnets. Additionally, about 25 standing
spin wave modes are observed inside a micron-sized FeGe wedge, measured at room
temperature ( K). These modes also exhibit unidirectional
anisotropy
Spatially resolved GHz magnetization dynamics of a magnetite nano-particle chain inside a magnetotactic bacterium
Understanding magnonic properties of nonperiodic magnetic nanostructures requires real-space imaging of ferromagnetic resonance modes with spatial resolution well below the optical diffraction limit and sampling rates in the 5–100 GHz range. Here, we demonstrate element-specific scanning transmission x-ray microscopy-detected ferromagnetic resonance (STXM-FMR) applied to a chain of dipolarly coupled Fe3O4 nano-particles (40–50 nm particle size) inside a single cell of a magnetotactic bacterium Magnetospirillum magnetotacticum. The ferromagnetic resonance mode of the nano-particle chain driven at 6.748 GHz and probed with 50 nm x-ray focus size was found to have a uniform phase response but non-uniform amplitude response along the chain segments due to the superposition of dipolar coupled modes of chain segments and individual particles, in agreement with micromagnetic simulations
Biologically encoded magnonics
International audienceSpin wave logic circuits using quantum oscillations of spins (magnons) as carriers of information have been proposed for next generation computing with reduced energy demands and the benefit of easy parallelization. Current realizations of magnonic devices have micrometer sized patterns. Here we demonstrate the feasibility of biogenic nanoparticle chains as the first step to truly nanoscale magnonics at room temperature. Our measurements on magnetosome chains (ca 12 magnetite crystals with 35 nm particle size each), combined with micromagnetic simulations, show that the topology of the magnon bands, namely anisotropy, band deformation, and band gaps are determined by local arrangement and orientation of particles, which in turn depends on the genotype of the bacteria. Our biomagnonic approach offers the exciting prospect of genetically engineering magnonic quantum states in nanoconfined geometries. By connecting mutants of magnetotactic bacteria with different arrangements of magnetite crystals, novel architectures for magnonic computing may be (self-) assembled
Evaluation protocol for revealing magnonic contrast in TR-STXM measurements
We present a statistically motivated method to extract magnonic contrast from time-resolved scanning transmission x-ray microscopy (TR-STXM) measurements. TR-STXM is an element-specific method for resolving spin-dynamics in space and time. It offers nanometer spatial resolution and picosecond temporal resolution. The presented method makes it possible to obtain phase and amplitude profiles of spin-waves from STXM measurements. Furthermore, it allows for a rigorous transformation to reciprocal magnon k⃗-space, revealing k⃗-dependent magnon properties such as the magnon dispersion in three dimensions and for all directions of the magnetic anisotropy. We demonstrate our method using X-band ferromagnetic resonance on a micrometer-sized permalloy assembly