Giant magneto-optical Kerr rotation observed in CeS single crystals

Abstract

We present the magneto-optical polar Kerr spectra of CeS single crystals, measured at 1.5 K in a field of 10 T. These spectra are dominated by a sharp and giant negative Kerr rotation peak of -22.08\ifmmode^\circ\else\textdegree\fi{} detected at the photon energy of 3.04 eV. This peak is the second largest measured Kerr rotation (after the record of 90\ifmmode^\circ\else\textdegree\fi{} detected recently on CeSb) in spite of the low magnetic moment of 0.31${\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$/Ce achieved in the CeS crystal under the experimental conditions. From these values, we find that CeS has the largest observed specific Kerr rotation, which is as high as 71.23\ifmmode^\circ\else\textdegree\fi{}/${\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$. Similar sharp negative peaks were observed in the magneto-optical Kerr rotation spectra of CeSe and CeTe at 2.60 and 1.99 eV, respectively. All these Kerr rotation peaks arise from 4f\ensuremath{\rightarrow}5d transitions from the 4f component of a p-f mixed state, as understood from the transition energies and comparing the total weight of the off-diagonal conductivity with the sample magnetization.