Changes of FIR Reflectivity of HgSe:Cr in a Magnetic Field

Abstract

The results of FIR magnetoreflectivity of HgSe:Cr are presented. They are interpreted using a classical dynamic diełectric function.PACS numbers: 78.20. Ls, 78.30.Fs Diluted magnetic semiconduction are crystals in which one of the non-magnetic components is substituted in a controlled way by magnetic ions [1]. Currently, the main interest has shifted from manganese based compounds to crystals in which the cations are substituted by other transition metal ions, see for example, see for example [2]. In HgSe:Cr the Cr 2 + ion substitute Hg atoms in the zinc blende type host lattice.HgSe, having an inverted band structure is always n-type. The only possible way of investigating low-energy excitations in such a material is through reflectivity measurements. The considerable number of competing processes such as plasma-, phonon-and electron-related excitations can make it difficult to identify the origin of observed stuctures. However, for energy levels which can be tuned by an applied magnetic field, magnetospectroscopy can help to clarify the nature of the observed spectral features.The investigated samples had low concentrations of Cr, not exceeding several times 1018 cm-3 . Therefore for these crystals we do not expect to observe effects due to local vibrations and exchange interaction. The magnetoreflectivity measurements were performed in the spectral range 50-700 cm-1 in magnetic fields up to 20 T using a Fourier Transform Spectrometer which was connected via an outcoupling optic to either a superconducting coil or a Bitter magnet [3]. All measurements were done in the Faraday geometry with nonpolarized light at 2 K.(741)