We introduce a novel integrated hybrid plasmonic-photonic device for
all-optical switching and reading of nanoscale ferrimagnet bits. The racetrack
memory made of synthetic ferrimagnetic material with a perpendicular magnetic
anisotropy is coupled on to a photonic waveguide onto the indium phosphide
membrane on silicon platform. The device which is composed of a double V-shaped
gold plasmonic nanoantenna coupled with a photonic crystal cavity can enable
switching and reading of the magnetization state in nanoscale magnetic bits by
enhancing the absorbed energy density and polar magneto-optical Kerr effect
(PMOKE) locally beyond the diffraction limit. Using a three-dimensional
finite-difference time-domain method, we numerically show that our device can
switch and read the magnetization state in targeted bits down to ~100 nm in the
presence of oppositely magnetized background regions in the racetrack with
widths of 30 to 120 nm, clearly outperforming a bare photonic waveguide. Our
hybrid device tackles the challenges of nonlinear absorption in the waveguide,
weak PMOKE, and size mismatch between spintronics and integrated photonics.
Thus, it provides missing link between the integrated photonics and nanoscale
spintronics, expediting the development of ultrafast and energy efficient
advanced on-chip applications