BISTABLE SWITCHING OF NUCLEAR-POLARIZATION STATES IN GALLIUM OXIDE

The dynamics and the switching processes of bistable nuclear polarizat ion states in gallium oxide are studied. Conduction-electron spin reso nance of oxygen-deficient beta-Ga2O3 crystals exhibits a bistable Over hauser effect, observable from hysteresis of the resonance line when t he external magnetic field is swept up and down. The dynamics of bista bility are investigated by considering the electron spin system couple d to nuclear spins of gallium as a simple (S = 1/2, I = 1/2) pair syst em. In this representation, the dynamics can be visualized as the over damped motion of a fictitious particle (the spin system) in a potentia l with two minima, which are the stable steady states of the bistable system. The observed phenomena are related to the rate of displacement of the fictitious particle in the potential well, which is controlled by the nuclear relaxation time, and to the rate of modification of th e potential, which corresponds to the rate of variation of the control parameter. This model gives a simple physical image of bistable switc hing operations and accurate simulations of bistable-electron-spin-res onance spectra. Addressing of the system with rectangular pulses has b een demonstrated for two control parameters: the external magnetic fie ld and the incident microwave power.