Light-induced magnetization in Hg1−xCdxTe

Abstract

We report the first observation of light-induced magnetization in a diamagnetic II–VI semiconductor. By improving the sensitivity of the pick-up coil arrangement, while still using standard RF-SQUID techniques, the photomagnetization (PM) of excited spin-polarized conduction electrons was detected with a signal-to-noise ratio of 3 using circularly polarized CO laser radiation (500 mW/cm 2). The samples were epitaxially grown p-type Hg 1− x Cd x Te layers on (100) CdTe with compositions f x = 0.25 to x = 0.29. The onset of PM occurs at the energy gaps, and the light-induced magnetic flux per illuminated sample area was 15–20 pT at maximum. PM is linear with laser intensity and vanishes for linear polarization of light. The spin-relaxation time which determines the maximum PM was deduced from the half-width of the depolarization curve applying a transverse magnetic field (Hanle effect). If the corresponding g ∗-factor ( g ∗ = -43 , for x = 0.28) was taken from band structure calculations, the relaxation of PM is obviously determined by Auger lifetime recombination processes for carrier energies smaller than the LO-phonon energy, and by Elliott-Yafet spin relaxation for energies above this threshold. The measurements were performed at a fixed temperature T = 2 K.