Magnetooptical Faraday and Kerr effects in nanosized BiYIG/GGG structures

• Magnetooptical Faraday and Kerr effects are studied in the nanosized BiY 2 Fe 5 O 12 films on the Gd 3 Ga 5 O 12 substrates. • The specific Faraday rotation for the nanosized Bi 0.5 Y 1.5 Fe 5 O 12-δ films reaches about 140000 deg/cm close to that for bulk BiY 2 Fe 5 O 12 . • Defining the magnetooptical parameters and Verdet constant for the Gd 3 Ga 5 O 12 substrate permits to separate correctly the substrate contribution. Magnetooptical Faraday and Kerr effects are studied in the nanosized BiY 2 Fe 5 O 12 films within the spectral region of 1.3 eV< E <4.5 eV and magnetic fields of up to 10 kOe. It is shown that the thin-films BiY 2 Fe 5 O 12 with the thicknesses ranging from 5 to 51 nm obtained by magnetron sputtering on the single-crystalline Gd 3 Ga 5 O 12 substrates have high magneto-optical quality. The specific Faraday rotation for the nanosized Bi 0.5 Y 1.5 Fe 5 O 12-δ films reaches about 140000 deg/cm close to that for bulk BiY 2 Fe 5 O 12 . Meanwhile, the polar Kerr effect reaches about 30 min within the range of 1.6 eV–4.1 eV at the magnetic fields above 2 kOe. It is shown that the strong paramagnetic contribution of Gd 3 Ga 5 O 12 substrates significantly affects the Faraday and Kerr effect for the films. The defining of magnetooptical parameters and Verdet constant for the Gd 3 Ga 5 O 12 substrate permitted to separate the substrate contribution and reveal peculiarities of spectral dependences of both Faraday and Kerr effects for magnetic films of various thicknesses. The estimated critical thickness of the film-substrate interface region is as large as 35 lattice constants of BiY 2 Fe 5 O 12 . It is shown that the magnetooptical effects for the thin films with the thickness above the critical one correspond to those for bulk BiY 2 Fe 5 O 12 . For samples with the smallest thicknesses of the film (5 nm) the contributions from magnetically dead and magnetically passive layers lead to a drastic reduction in the observable Faraday and Kerr effects with a dominating contribution from the substrate. The high density of displacement dislocations at the film-substrate interface leads to the decrease the magnetooptical quality of the nanosized films.