Efficient wavelength conversion of exchange magnons below 100 nm by magnetic coplanar waveguides

Abstract

Exchange magnons are essential for unprecedented miniaturization of GHz electronics and magnon-based logic. However, their efficient excitation via microwave fields is still a challenge. Current methods including nanocontacts and grating couplers require advanced nanofabrication tools which limit the broad usage. Here, we report efficient emission and detection of exchange magnons using micron-sized coplanar waveguides (CPWs) into which we integrated ferromagnetic (m) layers. We excited magnons in a broad frequency band with wavelengths λ down to 100 nm propagating over macroscopic distances in thin yttrium iron garnet. Applying time-and spatially resolved Brillouin light scattering as well as micromagnetic simulations we evidence a significant wavelength conversion process near mCPWs via tunable inhomogeneous fields. We show how optimized mCPWs can form microwave-tomagnon transducers providing phase-coherent exchange magnons with λ of 37 nm. Without any nanofabrication they allow one to harvest the advantages of nanomagnonics by antenna designs exploited in conventional microwave circuits.

Spin-wave spectroscopy of individual ferromagnetic nanodisks

“…In addition, the capability of FEBID to deposit magnetic layers with pre-defined properties onto conventional microwave circuits 17 makes it a valuable fabrication tool for nanomagnonics requiring microwave-to-magnon transducers for excitation and detection of phase-coherent exchange magnons with λ below 50 nm. 52 Finally, a modified version of the described microwave detection approach could be useful in studies of low electrical signal spin torque oscillators. 65…”

“…Such spin waves are appreciably influenced by the exchange interaction and are, in particular, objects of current investigations in nanomagnonics 50 aiming at the operation with fast, exchange-dominated spin waves. 27,51,52 Here, we demonstrate spatially resolved spin-wave spectroscopy for the assessment of magnetic properties of individual circular magnetic elements with radii down to 100 nm. Employing a coplanar waveguide whose 2 × 4 μm 2 -large active part is placed over a movable substrate with well-separated circular magnetic nanoelements we detect standing spin-wave resonances from individual 40 nm-thick CoFe-FEBID nanodisks.…”

Nanoscale magnonic Fabry-Pérot resonator for low-loss spin-wave manipulation

“…For static dipolar coupling, induced changes of the effective magnetic field within the YIG layer alter the propagation of spin waves 16 . Nonuniformities in the effective magnetic field can also be exploited for short-wavelength spin-wave emission 17 . Because of the static nature of the interaction in these examples, the effects extend over a broad frequency range.…”

Nanoimaging of Ultrashort Magnon Emission by Ferromagnetic Grating Couplers at GHz Frequencies

“… 20 To overcome this restriction and excite spin waves (SWs) with a wavelength λ much smaller than the size of the CPW is the subject of intense research. 21 Recently ultrashort SWs (magnons) were emitted by nanoscale spin textures which were irradiated by microwave fields. 22 − 25 Such spin textures required metallic multilayer stacks which are generally prone to large magnon damping, however.…”