Recent experiments have shown that the magnon velocity over nanoscale distancesin certain antiferromagnetic materials, with NiO in particular, far exceeds the previous theoretical maximum. Antiferromagnetic insulators are excellent candidatesfor spintronic nanodevices due to their exceptionally low energy dissipation, whichcould benefit the future speed at which information is stored. These magnons,which have since been dubbed ”superluminous-like magnons”, are classically notexpected, and it is hypothesized that the presence of a damping term in the equation of motion of the magnetic moment accounts for this anomalous behaviour.In this work, spin dynamics simulations are done using the UppASD software package in order to verify the existence of these superluminous-like magnons, where themagnon velocity in NiO is determined through a variety of ways. Analyzing simulated magnon spectra around high-symmetry points where the dispersion is linearallows for an extraction of magnon velocities, which shows no abnormal behaviourfor bulk NiO, as well as for large wavelength (low energy) magnons. Other ways todetermine the magnon velocity have been performed by studying the propagationof magnons that are excited through various methods. These studies also show thatthe magnon velocity does not far exceed the previous theoretical limit. While thesemagnons propagate slightly faster than they would in bulk, it is shown that thesemagnons very rapidly decelerate to their known bulk speeds.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-494218 |
| Date | January 2023 |
| Creators | van Poppelen, Jannes |
| Publisher | Uppsala universitet, Materialteori |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | FYSAST ; FYSMAS1198 |
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