A nuclear magnetic resonance (NMR) study has been carried out on a GaAs/Al0.3Ga0.7As multiple-quantum-well sample, containing two-dimensional (2D) electron layers, in the quantum Hall regime. The spin polarization P of 2D electrons is determined from the hyperfine shift of 69.71Ga nuclei, measured by standard pulsed NMR. We have used the tilted-magnetic field technique to investigate the effect of an increasing Zeeman energy on P around Landau level filling factor v=1. Mostly on the basis of measurements performed at B=17 T and T=1.5 K, we conjecture that in the high-B and low-T limit, P(v) follows the predictions of the noninteracting-electron model. The low-temperature P(v=1) is found to be far below the expected full polarization, and the observed nuclear spin-lattice relaxation rate is not reduced, in contrast to the observations by optically pumped NMR. The two techniques obtain different results only close to v=1, and the reason why remains unclear; simple explanation in terms of the nonuniform electron density does not seem satisfactory.
|Original language||English (US)|
|Number of pages||9|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Aug 15 2001|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics