The effect of a longitudinal magnetic field on the optical spin orientation and spin-dependent recombination in dilute nitrides GaAsN has been studied for the first time. We have found that intensity $I$ and circular polarization degree $\rho$ of the edge photoluminescence, excited in GaAsN alloys by circularly polarized light at room temperature, grow substantially in the longitudinal magnetic field $B$ of the order of 1 kG. This increase depends on pump power, and, in the region of weak or moderate powers, the $I$ and $\rho$ can reach a twofold value. We included the magnetic-field suppression of spin relaxation of the deep paramagnetic centers in the two-charge-state model, which considers the spin-dependent recombination of spin-polarized free electrons on the centers. The modified model describes qualitatively the rise of $\rho$ and $I$ in a magnetic field under different pump intensities. Experimental dependences $\rho \left(B\right)$ and $I\left(B\right)$ are shifted with respect to zero of the magnetic field by a value of $\sim$200 G, while the direction of the shift reverses with change of the sign of circular polarization of pumping. As a possible cause of the discovered shift we consider the Overhauser field, arising due to the hyperfine interaction of an electron bound on a center with nuclei of the crystal lattice in the vicinity of the center.

• Received 7 July 2011

DOI:https://doi.org/10.1103/PhysRevB.85.035205