The demand for faster magnetization switching speeds and lower energy consumption has driven the field of spintronics in recent years. Whereas spin-transfer-torque and spin-orbit-torque interactions exemplify the potential of electron-spin-based devices and memory, the switching speed is limited to the ns regime by the precessional motion of the magnetization. All-optical magnetization switching, based on the inverse Faraday effect, has been shown to be an attractive method for achieving magnetization switching at ps speeds. Successful magnetization reversal in thin films has been demonstrated by using circularly polarized light. However, a method for all-optical switching of on-chip nanomagnets in high density memory modules has not been described. In this work we propose to use plasmonics, with CMOS compatible plasmonic materials, to achieve on-chip magnetization reversal in nanomagnets. Plasmonics allows light to be confined in dimensions much smaller than the diffraction limit of light. This in turn, yields higher localized electromagnetic field intensities. In this work, through simulations, we show that using surface plasmon resonances, it is possible to couple light to nanomagnets and achieve significantly higher opto-magnetic field values in comparison to free space light excitation for the same incident intensity. We use two well-known magnetic materials Bismuth Iron Garnet (BIG) and Gadolinium Iron Cobalt (GdFECo) and couple these nanomagnets to a plasmonic resonator made of Titanium Nitride. Our simulation results show 10 times enhancement in the opto-magnetic field for BIG and about 3 times for GdFeCo in the coupled structure compared to free-space excitation. Our simulations also show the possibility of having in-plane components of the opto-magnetic field in the coupled structure which might prove beneficial for switching in nanomagnets with canted magnetization.
Aveek Dutta, Alexander V. Kildishev, Vladimir M. Shalaev, Alexandra Boltasseva, and Ernesto E. Marinero, "Surface-plasmon optomagnetic field enhancement for all-optical magnetization switching (Conference Presentation)," Proc. SPIE 10535, Integrated Optics: Devices, Materials, and Technologies XXII, 105351I (Presented at SPIE OPTO: February 01, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2288895.5751551029001.
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