Kavli Affiliate: Toeno Van Der Sar
| First 5 Authors: Brecht G. Simon, Samer Kurdi, Joris J. Carmiggelt, Michael Borst, Allard Katan
| Summary:
Nitrogen-vacancy (NV) magnetometry is a new technique for imaging spin waves
in magnetic materials. It detects spin waves by their microwave magnetic stray
fields, which decay evanescently on the scale of the spin-wavelength. Here, we
use nanoscale control of a single-NV sensor as a wavelength filter to
characterize frequency-degenerate spin waves excited by a microstrip in a
thin-film magnetic insulator. With the NV-probe in contact with the magnet, we
observe an incoherent mixture of thermal and microwave-driven spin waves. By
retracting the tip, we progressively suppress the small-wavelength modes until
a single coherent mode emerges from the mixture. In-contact scans at low drive
power surprisingly show occupation of the entire iso-frequency contour of the
two-dimensional spin-wave dispersion despite our one-dimensional microstrip
geometry. Our distance-tunable filter sheds light on the spin-wave band
occupation under microwave excitation and opens opportunities for imaging
magnon condensates and other coherent spin-wave modes.
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