Second-harmonic generation in the magnetic semiconductor (Cd, Mn)Te

Abstract

A phenomenological analysis and experimental observations of second-harmonic generation (SHG) in magnetic semiconductors with zinc blende crystal structure ¯43m in zero and nonzero magnetic fields are presented. A magnetic field reduces symmetry and gives rise to new SHG components. SHG transmission spectra were studied in Cd_1−xMn_xTe with x = 0.24, 0.35, and 0.40. At low temperatures a narrow SHG band at 1.98 eV in the vicinity of the fundamental bandgap was observed in a (110) sample with x = 0.24. The band disappears with a temperature increase when short-range magnetic ordering vanishes. Below the bandgap a SHG signal is found that varies strongly as a function of magnetic field. We relate this phenomenon to magnetic linear birefringence and the shift of the bandgap in a magnetic field.