Effect of magnetic field on tunneling systems in glasses

The effect of a magnetic field on two-level tunneling systems in dielectric glasses originates from the magnetic-field-induced rotation of nuclear spins and the ensuing rearrangement of ordered regions (clusters) in the glass structure. This process accounts for the observed variation of both the spontaneous-polarization echo amplitude and the dielectric constant in a magnetic field at low temperatures. The proposed theory is compared with experiment.