Surface-plasmon opto-magnetic field enhancement for all-optical magnetization switching

Abstract

The demand for faster magnetization switching speeds and lower energy consumption has driven the field of spintronics in recent years. The magnetic tunnel junction is the most developed spintronic memory device in which the magnetization of the storage layer is switched by spin-transfer-torque or spin-orbit torque interactions. Whereas these novel spin-torque interactions exemplify the potential of electron-spinbased 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 localized surface plasmon resonances, it is possible to couple light to nanomagnets and achieve significantly higher optomagnetic field values in comparison to free space light excitation.

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]N Films

“…[ 43,50 ] Moreover, designs in which the ferromagnetic layer itself is patterned into arrays, channels, or racetrack architectures could minimize radiative damping of p m modes. [ 56–58 ]…”

“…[43,50] Moreover, designs in which the ferromagnetic layer itself is patterned into arrays, channels, or racetrack architectures could minimize radiative damping of p m modes. [56][57][58] In summary, independently tuning Mie-type dipolar resonances within dielectric metasurfaces to control the field extrusion outside of the nanoantennas enables locally confined, multifold enhancement in electric field rotation within proximal ferromagnetic films. Rotational enhancement at p e resonances gives rise to tunable MO responses that were experimentally validated by measuring dissymmetric reflection and transmission of CPL, and that enhance angular variation of Faraday and polar Kerr rotations over unpatterned films.…”

Switchable plasmonic routers controlled by external magnetic fields by using magneto-plasmonic waveguides

“…We note that the experimentally observed gyration values of 0.03 or 0.06 for Bi-substituted iron garnet (BIG) have been reported in Ref., 35 in the Table 1 of Ref. 36 and in the Methods of Ref. 37 We assume a bending radius of 300 nm for which the numerical simulation shows a small value of the bending loss of 1.2%.…”

Plasmonic layer-selective all-optical switching of magnetization with nanometer resolution

“…In addition, upon illuminating a dielectric/metallic interface with p-polarized light, a surface plasmon polariton (SPP) can be excited 15 . The optical field enhancement associated with SPPs could offer a pathway towards an even smaller energy cost of all-optically writing a bit 13,14,16 . At the same time, by confining the optical field using a plasmonic antenna, the optically-addressed region of magnetization has been successfully downscaled to length scales on the order of 50 nm 17 .…”