Tatyana V. Mikhailova

The experimental results of studying the influence of ion etching of cation-substituted iron-garnets single-crystal films on their structural, magnetic, optical and magneto-optical properties are presented in article. It has been shown, that the ionic etching of the surface of single-crystallin garnets significantly decrease the surface roughness. An analysis of the domain structure, ferromagnetic resonance spectra, and magneto-optical hysteresis loops in a bismuth-substituted iron-garnet epitaxial film during layer-by-layer ion etching showed the presence of three different layers, the state of which changes relative to the compensation point, and the interlayer interfaces correspond to the transition through the compensation point. It has been shown, that the position of interlayer interfaces can be changed by the sample temperature changing. The investigation of optical and magneto-optical characteristics showed that in single-crystallin (epitaxial) films of iron-garnets the ion etching does not impair optical transmission and does not destroy the garnet structure up to a thickness of tens of nanometers (the Faraday effect is retained).

The experimental results of a study of the influence of ion etching of single-crystal films of cation-substituted iron-garnets on their structural, magnetic, optical, and magneto-optical properties are presented. It is shown that the ion etching of single-crystal garnets significantly reduces the surface roughness. Analysis of the domain structure, ferromagnetic resonance spectra, and magneto-optical hysteresis in the epitaxial film of bismuth-substituted iron-garnet during layer-by-layer ion etching shows the presence of three different layers, the state of which changes relative to the compensation point and the interfaces of the layers correspond to the transition through the compensation point. It is shown that the position of the layer interfaces can be varied by changing the temperature of the sample. A study of optical and magneto-optical characteristics shows that in single-crystal (epitaxial) films of iron-garnets, ion etching does not worsen optical transmission and does not destroy the garnet structure down to a thickness of tens of nanometers (the Faraday effect is preserved).

The phenomena of magneto-optical polarization rotation and circular magnetic dichroism are well known in the Faraday configuration. We present another effect, an odd magneto-optical linear dichroism, arising in nanostructures with polarization-dependent mode Q-factors and magneto-optical components. It reveals itself as the magneto-optical modulation of light intensity for the two opposite magnetization directions in the Faraday configuration. The effect was demonstrated on a magnetophotonic crystal with a cavity mode, the polarization-dependent Q-factor of which is due to oblique incidence. For a polarization angle of 60° (or 120°) and an angle of incidence around 60°, the magneto-optical intensity modulation maximizes and reaches 6%.

It is widely known that the magneto-optical Faraday effect is linear in magnetization and therefore the Faraday angles for the states with opposite magnetizations are of opposite sign but equal in modulus. Here we experimentally study propagation of light through a one-dimensional all-garnet magnetophotonic crystal to demonstrate an asymmetric Faraday effect (AFE) for which Faraday angles for opposite magnetic states differ not only in sign but in the absolute value as well. AFE appears in the vicinity of the cavity resonance for an oblique incidence of light which plane of polarization is inclined to the incidence plane. Under proper incidence and polarization angles the magnitude of AFE could be very large reaching 30% of the absolute value of the Faraday effect. The effect originates from the difference in Q-factors for p- and s- polarized cavity modes that breaks the symmetry between the two opposite directions of polarization rotation. The discovered AFE is of prime importance for nanoscale magnonics and optomagnetism.

A magnetophotonic Tamm structure with a bilayer film of Bi-substituted iron garnets (Bi:IG) with a significant magneto-optical (MO) response, placed in microcavity, and Tamm plasmon-polaritons (TPP) excited at the interface of the Au layer, were proposed. Optical and MO spectra of the hybrid state were investigated theoretically and experimentally in Faraday effect geometry at a normal incidence of the light wave. Anticrossing behavior of the TPP and Fabry-Perot resonances and dependence of spectral splitting on their hybrid state on the thickness of the Au layer was shown. By varying the thickness of the top SiO₂ layer in the structure, the modifications of spectra on the TPP spectral position were described in detail. The results can be used to design tunable MO devices and sensors.

The work presents the results of investigation of hybrid states of Tamm plasmon polaritons (TPP) in magnetoplasmonic nanostructures (MPNS) based on Bi-substituted iron garnet (Bi:IG) and Au layers and nanoparticles. To study the interaction of resonances, two MPNS were synthesized with gold-coated dielectric layer of gradient thickness. It was shown the difference in properties of model MPNS with hybrid state of TPP – Fabry-Perot and a single TPP excitation. It was suggested to use the hybrid state to increase the sensitivity of optical sensors.

Magneto-optical microscopy is a widely used method for magnetic domain structure characterization. Faraday effect allows to investigate transparent magnetic samples. Magnetooptical microscopy has many advantages but also has a limitation caused by diffraction limit of the light. Authors proposed to improve optical resolution of magneto-optical microscopy by using aperture probe for lighting up the sample. Comparison of different types of probes was permed and aperture cantilever probe with carbon tip was chosen for the experiment. Authors show possibility to obtain not only magneto-optical contrast but also morphology information by detecting probe displacement caused by sample-probe interaction. Authors measured Bi:YIG-thin films by high resolution magneto-optical microscopy. Images of domain with subdomain structure and topography were obtained by proposed method.