TMOKE as efficient tool for the magneto-optic analysis of ultra-thin magnetic films

Abstract

Ultra-thin magnetic dielectric films are of prime importance due to their applications for nanophotonics and spintronics. Here we propose an efficient method for the magneto-optical investigation of ultra-thin magnetic films that allows one to access their state of magnetization and magneto-optical properties. It is based on the surface-plasmon-polariton-assisted transverse magneto-optical Kerr effect (TMOKE). In our experiments sub-100nm-thick bismuth-substituted lutetium iron-garnet films covered with a plasmonic gold grating have been analyzed. The excitation of surface plasmon-polaritons provides resonance enhancement of TMOKE up to 0.04 and makes it easily detectable in experiment. For films thicker than 40 nm the TMOKE marginally depends on the film thickness. Further decrease of the film thickness diminishes TMOKE since for such thicknesses the surface plasmon-polariton field partly penetrates inside the nonmagnetic substrate. Nevertheless, the TMOKE remains measurable even for few-nm-thick films, which makes this technique unique for the magneto-optical study of ultra-thin films. Particularly, the proposed method reveals that the off-diagonal components of the magnetic film permittivity tensor grow slightly with the reduction of the film thickness.Currently, ultra-thin ferrimagnetic dielectric films are of significant interest due to their applications in nanophotonics, magnonics and spintronics [1][2][3][4][5][6]. Magnetic dielectrics like bismuthsubstituted iron-garnets have outstanding optical properties in the near infrared where they evince low optical absorption and a relatively large magneto-optical response [7][8][9][10]. Practical use of spintronic devices for magnetic information recording requires magnetic field confinement in the

All-dielectric magnetic metasurface for advanced light control in dual polarizations combined with high-Q resonances

“…It is worth noting that propagating modes (such as guided or surface plasmon-polariton modes) are more promising, since their wavevector is non-reciprocally modified by the external magnetic field 31 in contrast to the localized modes (localized plasmons or Mie modes) in different kinds of nanoantennas, demonstrating a very moderate TMOKE increase 32 , 33 although both of them exhibit strong light localization inside the nanostructure 34 , 35 . Thus, magnetoplasmonic crystals consisting of a periodic 1D or 2D metallic grating and a magnetic film are one of the most efficient nanostructures providing a significant enhancement of the light modulation both in reflected and transmitted light 14 , 36 – 38 . However, it is important that observation of the magneto-optical effects in magnetoplasmonic structures is accompanied by a significant decrease of the base signal due to high absorption in metals, also leading to resonance broadening.…”

High-Refractive-Index Materials for Giant Enhancement of the Transverse Magneto-Optical Kerr Effect

“…In practice, many of these applications are challenged by extremely weak TMOKE signals in ferromagnetic metals (~10 −3 ) [24]. This limitation is traditionally beaten through the magnetoplasmonic effect, i.e., the combination of MO and plasmonic effects [1][2][3][4][5][6][7]. In this approach, the strongly enhanced near-field amplitudes of surface plasmon resonances (SPRs) are distributed inside an adjacent MO layer to improve the MO activity.…”

Controlling the Transverse Magneto-Optical Kerr Effect in Cr/NiFe Bilayer Thin Films by Changing the Thicknesses of the Cr Layer

“…In general, MOKE is of interest for light modulation, with a magnetic field that typically requires MOKE enhancement by interferometric [14] or resonance [2,15] methods. On the other hand, magneto-optical effects provide a powerful nondestructive technique to investigate magnetization behavior in magnetic nanostructures, such as measuring magnetic hysteresis loops and imaging the magnetic domains [16,17]. The transverse magneto-optical Kerr effect (TMOKE) is a simple, economical and sensitive method to measure thin magnetic films in comparison with superconducting quantum interference device (SQUID) and Vibrating Sample Magnetometer (VSM) [18].…”