Microwave helicon propagation and helicon-excited electron paramagnetic resonance inHg1−xMnxTe

Abstract

Helicon waves can be exploited for the study of electron paramagnetic resonance (EPR) of localized spins in high-conductivity semiconductors when the free carriers have a small effective mass and a high mobility. It is shown that in an electron plasma helicons have precisely the polarization required to elicit EPR, and the plasma background then actually enhances the resonance intensity. Helicon-excited EPR is investigated at 35.0 GHz in ${\mathrm{Hg}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$, a narrow-gap semiconductor with localized ${\mathrm{Mn}}^{++}$ spins, using transmission experiments. The effect is investigated as a function of temperature, manganese concentration, and free-electron concentration. Microwave helicon transmission also provides a measure of the free-electron concentration and mobility. Considerable attention is given to the determination of these electrical transport parameters in ${\mathrm{Hg}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$ from the helicon measurements. It is shown that, when electrical parameters are known, the value of the dynamic magnetic susceptibility of the ${\mathrm{Mn}}^{++}$ spin system can also be determined in the experiment.