  The quantum-mechanical calculations of intensities and time moments of
appearance of multiple spin echo signals of excitation of nuclear spin system
of magnet by two arbitrary width radio-frequency pulses were carried out. This
method was used by us earlier at consideration of multiple-pulse analogs of
single-pulse echo in multidomain magnets upon sudden jumps of the effecting
magnetic field in the rotating coordinate system during the action of
radio-frequency pulse. The formation mechanisms of echo signals are discussed.
The appearance of four primary stimulated echo signals is predicted. The total
number of echo signals at fixed parameters of radio-frequency pulses does not
exceed thirteen ones. Theoretical conclusions are in compliance with
experiments carried out on lithium ferrite. As it was established by us earlier
in this magnetic dielectric, in difference from ferrometals, it is observed
very short relaxation times of single-pulse and two-pulse stimulated echoes,
and the contribution of radio-frequency pulse fronts distribution mechanism is
insignificant. For this reason lithium ferrite is a good material for the
experimental verification of theoretical conclusions in experimental conditions
most close to the theoretical model.
