Polar Kerr rotation in Co-doped hexagonal ferrites

The spectral dependencies of the polar Kerr rotation on a series of cobalt- and titanium-substituted single crystals of barium hexaferrites were measured in the visible and near-infrared region. Kerr rotations obtained on polished and etched (0001) surfaces were superior to the spectra obtained on the natural growth planes. The largest Kerr rotations (exceeding 4° at wavelengths of about 1800 nm) were found for molar concentrations of cobalt that were approximately equal to 0.04. Kerr-rotation hysteresis loops displayed small coercive force (<500 Oe) and small remanent values with a strong unidirectional character