Far-infrared observation of the electric-dipole spin resonance of donor electrons inCd1−xMnxSe

Abstract

Far-infrared (FIR) measurements of electric-dipole spin resonance (EDSR) of donor-bound electrons in ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$ ($x=0.10 \mathrm{and} 0.20$ are reported. The EDSR transition is allowed in ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$ by the combined effects of spin-orbit interaction and the acentric uniaxial symmetry of this wurtzite system. The far-infrared EDSR is observed at magnetic fields of the order of 1 T, indicating extremely large effective $g$ factors (in excess of 100) due to contributions from the exchange interaction between the band electrons and the localized magnetic moments. Measurements as a function of temperature and frequency reveal a strong temperature dependence of the $g$-factors, and a dramatic increase in the strength of EDSR with frequency. Studies with linear and circular polarization were used to determine the selection rules governing EDSR, as well as the sign of the exchange integral for the conduction band of ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$. EDSR is observed only in samples characterized by low resistivities (\ensuremath{\sim}1 \ensuremath{\Omega} cm at 77 K), with donor concentrations in the range of ${10}^{16}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. In addition to EDSR, the FIR magnetotransmission spectra show several other interesting features, which are interpreted in terms of conduction-electron cyclotron resonance and magnetic field dependence in the $1s\ensuremath{\rightarrow}2p$ transitions of the donor levels.