Abstract
As a potential route towards beyond CMOS computing magnonic waveguides show outstanding properties regarding fundamental wave physics and data transmission. Here, we use time resolved scanning transmission X-ray microscopy to directly observe spin waves in magnonic permalloy waveguides with nanoscale resolution. Additionally, we demonstrate an approach for k-vector selective imaging to deconvolute overlapping modes in real space measurements. Thereby, we observe efficient excitation of symmetric and antisymmetric modes. The profiles of higher order modes that arise from sub-micron confinement are precisely mapped out and compared to analytical models. Thus, we lay a basis for the design of multimode spin wave transmission systems and demonstrate a general technique for k-specific microscopy that can also be used beyond the field of magnonics.
Highlights
Downscaling magnonic waveguides to the nanometer regime introduces different physics than in larger structures,[24] e.g. interference of lateral standing spin waves by spatial confinement leading to higher order modes has been predicted theoretically.[25]
By using a homogeneous radio frequency (RF) field at fCW, spin waves can be excited at these regions resulting in directed emission within the waveguide
The width of the signal line is much larger compared to the waveguide width, the distribution of the RF field BCW can be assumed homogeneous across the lateral dimension
Summary
Magnons, which describe the quanta of spin waves, have been recently investigated in terms of new fundamental physics at the nanoscale and their potential for future data communication applications.[1,2,3,4,5,6,7,8] Due to a bottleneck of CMOS transistor miniaturization, magnonics are increasingly discussed as a complementary technology.[3,4,8] Futhermore, there are many interesting analogies to photonics, like guiding of propagating waves or evanescent wave phenomena.[9,10,11,12,13] Especially, magnonic waveguides were discussed in literature revealing outstanding fundamental characteristics and useful properties regarding data transmission.[4,10,14]The equivalent to magnonic waveguides in photonics is the concept of single- and multimode propagation in fiber optics.[15]. Micromagnetic simulations and experiments have shown multiple applications of magnonic waveguides as majority gates, couplers or frequency filters.[8,20,21,22] a spin wave spectrum analyzer that could be used for demultiplexing has been proposed.[23] Downscaling magnonic waveguides to the nanometer regime introduces different physics than in larger structures,[24] e.g. interference of lateral standing spin waves by spatial confinement leading to higher order modes has been predicted theoretically.[25] Guslienko et al already showed calculations of effective dipolar boundary conditions in a magnetic stripe geometry.[26]
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