Ultrafast Magnetism Enabled by Nanoplasmonics

The quest to improve the density, speed and energy efficiency of magnetic memory storage has led to the exploration of new ways of optically manipulating magnetism at the ultrafast time scale, in particular in ferrimagnetic alloys. While all-optical magnetization switching is well-established on the femtosecond timescale, lateral nanoscale confinement and thus the potential significant reduction of the size of the magnetic element remains an outstanding challenge. Thus magnetic memory combining plasmonics and magnetism is poised to dramatically increase the bit density and energy efficiency of light-assisted ultrafast magnetic storage, thanks to nanoplasmon-driven enhancement and confinement of light [1]. I highlight several recent examples from our work, were we employ plasmon nanoantennas to either funnel electromagnetic energy into ferrimagnetic films assisting the demagnetization at the nanoscale [2], or to build hybrid plasmon-ferrimagnet nanoantennas forming magnetophotonic surface crystals [3,4]. The produced robust magnetophotonic architectures could serve as the building blocks for plasmon-assisted all-optical magnetization switching technology in ferrimagnetic rare earth – transition metal alloys that are the prime candidates to realize in practice femtomagnetic memory storage. In addition, the produced platforms could help realizing the conceptually new high-resolution light incidence direction sensors or systems with multistate ultrafast demagnetization states, potentially opening up for so-far-unforeseen nanomagnetic neuromorphic-like devices operating at femtosecond timescales controlled by light.<br/>[1] N. Maccaferri et al., Nanoscale magnetophotonics, <b><i>J. Appl. </i></b><b><i>Phys.</i></b><i>, </i>127, 080903 (2020).<br/>[2] K. Mishra et al., Ultrafast demagnetization in a ferrimagnet under electromagnetic field funneling, <b><i>Nanoscale</i></b> 13, 19367 (2021) <i>(journal cover).</i><br/>[3] R. M. Rowan-Robinson et al., Direction-sensitive magnetophotonic surface crystals, <b><i>Adv. Photon. Research</i></b> 2100119 (2021) <i>(journal cover).</i><br/>[4] K. Mishra et al., Ultrafast Demagnetization Control in Magnetophotonic Surface Crystals, <i>under review</i> (2022).