Magnetic Polaron of Gd₂S₃ Studied by Infrared Spectroscopy under Magnetic Field

Abstract

Reflectivity spectra of a magnetic semiconductor Gd₂S₃ (=Gd_3-x\Box_xS₄, where \Box denotes vacancy and x≅ 1/3) have been measured in the photon energy range from 2 meV to 0.5 eV at 14 K under magnetic field up to 5 tesla. The energy gap of about 7 meV at 0 tesla was observed to become narrow as the magnetic field increases and to collapse at 3.3 tesla. The origin of the energy gap is attributed to the trapped magnetic polaron. Another absorption band around 0.1 eV of which origin has been unclear is concluded to be the deep state of the magnetic polaron because it was shifted by the magnetic field.