  We analyze nonlinear magneto-optical rotation (NMOR) in rubidium vapor
subjected to continuously-scanned magnetic field. By varying magnetic-field
sweep rate, a transition from traditionally-observed dispersive-like NMOR
signals (low sweep rate) to oscillating signals (higher sweep rates) is
demonstrated. The transient oscillatory behavior is studied versus light and
magnetic-field parameters, revealing a strong dependence of the signals on
magnetic-sweep rate and light intensity. The experimental results are supported
with density-matrix calculations, which enable quantitative analysis of the
effect. Fitting of the signals simulated versus different parameters with a
theoretically-motivated curve reveals presence of oscillatory and static
components in the signals. The components depend differently on the system
parameters, which suggests their distinct nature. The investigations provide
insight into dynamics of ground-state coherence generation and enable
application of NMOR in detection of transient spin couplings.
