Nuclear polarization by optical pumping in InP:Fe above liquid nitrogen temperature
Hyperpolarized nuclear spins are observed in optically pumped iron-doped InP from 70 K to 140 K. P-31 NMR was carried out at 9.28 T (159.8 MHz) during optical excitation with circularly polarized light, using a laser diode (lambda-830 nm) as a source. The enhancement of the nuclear spin polarization by optical pumping at 70 K is estimated to be about 34 for those nuclei in the region of the sample absorbing light. This enhancement decreases with increasing temperature. As the direction of the enhanced nuclear spin polarization is found parallel or antiparallel to the travelling direction of the sigma(+) or sigma(-), the contact hyperfine interaction is dominant compared to the dipolar hyperfine interaction. (C) 2015 Elsevier Inc. All rights reserved.