Abstract
Creating sub-micron hotspots for applications such as heat-assisted magnetic recording (HAMR) is a challenging task. The most common approach relies on a surface-plasmon resonator (SPR), whose design dictates the size of the hotspot to always be larger than its critical dimension. Here, we present an approach which circumvents known geometrical restrictions by resorting to electric field confinement via excitation of a gap-mode (GM) between a comparatively large Gold (Au) nano-sphere (radius of 100 nm) and the magnetic medium in a grazing-incidence configuration. Operating a lambda = 785 nm laser, sub-200 nm hot spots have been generated and successfully used for GM-assisted magnetic switching on commercial CoCrPt perpendicular magnetic recording media at laser powers and pulse durations comparable to SPR-based HAMR. Lumerical electric field modelling confirmed that operating in the near-infrared regime presents a suitable working point where most of the light's energy is deposited in the magnetic layer, rather than in the nano-particle. Further, modelling is used for predicting the limits of our method which, in theory, can yield sub-30 nm hotspots for Au nano-sphere radii of 25-50 nm for efficient heating of FePt recording media with a gap of 5 nm. Published by AIP Publishing.
| Original language | English |
|---|---|
| Article number | 143102 |
| Number of pages | 8 |
| Journal | Journal of Applied Physics |
| Volume | 123 |
| Issue number | 14 |
| DOIs | |
| Publication status | Published - 14 Apr 2018 |
Funding
R.McC. acknowledges support from the U.S.-Ireland Partnership R&D Project USI 043 and EPSRC Grant No. EP/1038411/1. G.S. and D.O. acknowledge support from the Israeli Centers of Research Excellence Program and the Crown Center of Photonics. G.S. would like to express his gratitude to Daniel Friedrich (University of Würzburg) for help with AFM imaging. The authors are grateful to Matthew Doherty (Queen's University Belfast) for establishing a first theoretical description of the experimental system using Comsol and to Paul Dawson (Queen's University Belfast) for useful discussions on gap modes in the context of STM.