)Department of Physics, Lomonosov Moscow State University, 119992 Moscow, Russia.
)In the discussion, I will review recent experimental and theoretical results on magnetooptical properties of nanostructured magnetic materials, focusing on giant magnetooptical effects in some magnetic granular alloys and discontinuous multilayers. The enhanced magnetooptical effect in magnetic circular dichroism, Faraday rotation and transversal Kerr effect spectra of diluted granular alloys MnAs:GaAs has been discovered [1]. The magnetooptical signal depends heavily on the size of MnAs nanoclusters, oscillates under variation of photon energy E and reaches maximum values at around E=1.75 and 1.2 eV. The origin of this effect is not well understood, within the effective-medium approach calculated values are 30 times smaller than in experiment.
The huge magnetooptical Kerr effect has been observed also in discontinuous multilayers Co/SiO2 at E= 3.0 eV and Co/Al2O3 at E= 2.7 eV [2]. The magnetooptical signal depends non-monotonically on granular size, thickness and type of insulator spacer, thickness of multilayers.
At last recently, the strong magnetorefractive effect in the infrared region of spectrum has been found in some granular metal-insulator alloys with tunnel-type magnetoresistance [3]. The change of reflectivity in applied magnetic field is more than 1%, that is two orders of magnitude larger than that for conventional magnetooptical effects.
The possible applications of giant magnetooptical effects are discussed.