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

Abstract

On-chip signal processing at microwave frequencies is key for modern mobile communication. When one aims at small footprints, low power consumption, reprogrammable filters, and delay lines, magnons in low-damping ferrimagnets offer great promise. Ferromagnetic grating couplers have been reported to be specifically useful as microwave-to-magnon transducers. However, their interconversion efficiency is unknown and real-space measurements of the emitted magnon wavelengths have not yet been accomplished. Here, we image with subwavelength spatial resolution the magnon emission process into ferrimagnetic yttrium iron garnet (YIG) at frequencies up to 8 GHz. We evidence propagating magnons of a wavelength of 98.7 nm underneath the gratings, which enter the YIG without a phase jump. Counterintuitively, the magnons exhibit an even increased amplitude in YIG, which is unexpected and due to a further wavelength conversion process. Our results are of key importance for magnonic components, which efficiently control microwave signals on the nanoscale.

Tunable Damping in Magnetic Nanowires Induced by Chiral Pumping of Spin Waves

“…Spin waves (SWs), or their quasiparticle magnons, − can be used to propagate and process information with low power dissipation because of the absence of a charge flow, and this feature offers plenty of functionalities for logic devices. − Besides coherent propagating SWs, incoherent spin current transport also facilitates promising development toward energy-efficient spintronics devices. − Spin pumping and spin Seebeck effect are significant for generating and manipulating spin current. − Previous works have been carried out and show that the additional damping exists in ferromagnetic film (FM) adjacent to normal metal (NM) film, where precessing magnetization in the FM layer injects a pure spin current (or transfers angular momentum) into the NM layer. ,− …”

Direct observation of multiband transport in magnonic Penrose quasicrystals via broadband and phase-resolved spectroscopy

“…Because of the low rotational symmetry, the formation of a complete magnonic bandgap is more challenging for MCs based on periodic lattices ( 20 ) than for quasicrystals, which can exhibit much higher rotational symmetry. The latter feature is advantageous also for multidirectional magnon emission in case of the magnonic grating coupler effect ( 21 – 24 ), which, however, has not yet been reported for 2D quasicrystals.…”

Xenon Plasma Focused Ion Beam Milling for Obtaining Soft X-ray Transparent Samples

“…Another approach to fabricate soft X-ray transparent samples is to use focused gallium ion beam (Ga FIB) milling in combination with mechanical grinding to remove substrate material until the samples are transparent in the soft X-ray regime [13][14][15][16][17][18]. While this technique marks an important milestone for X-ray transmission experiments, it is at the same time severely limited by the relatively low milling speed of the Ga FIBs used.…”