Discovery of 90 degree Magneto-optical Polar Kerr Rotation in CeSb

Abstract

We report the first discovery of 90\ifmmode^\circ\else\textdegree\fi{} magneto-optical Kerr rotation in CeSb at 1.5 K in a field of 5 T. This is 6.5 times more than the previous record rotation of 14\ifmmode^\circ\else\textdegree\fi{} and it is the absolute maximum observable rotation in a single reflection. Using newly derived equations for large rotations and ellipticities, the off-diagonal conductivity has been computed from the magneto-optical spectra and the optical spectra determined for the same external parameters. The spectra are discussed in terms of the field and temperature dependent ground state of CeSb.