Time-dependent absorption of gamma-radiation under high-frequency magnetic excitation of ⁵⁷Fe

We have studied the time dependence of Mössbauer absorption in a magnetically soft sample of Fe₁₈Ni₈₂ permalloy under the influence of a radio-frequency (r.f.) magnetic field. Absorption was measured as a function of the r.f. field phase at specific gamma-ray energies. We have shown that measuring the time dependence of absorption makes it possible to differentiate between purely magnetic and magnetoacoustic modulation mechanisms even in cases where clear distinction is not visible in conventional energy domain spectra.