Relaxation-stimulated resonances in Mossbauer absorption spectra under radiofrequency magnetic field excitation

A new type of resonant phenomena in the Mossbauer spectroscopy of soft magn etic materials in radiofrequency (rf) magnetic fields is predicted for the rf field frequencies related to those of components of the magnetic hyperfi ne structure via the parametric resonance condition. Resonant effects of th is kind are still unknown in physics; they are realized not at frequencies of transitions between the energy sub-levels of the ground or excited nucle ar states, which take place in conventional nuclear magnetic resonance, but at frequencies which are a combination of the frequencies of hyperfine tra nsitions. In this case a separation between the real energy levels can exce ed the value of the 'resonant' frequency by about 10 orders of magnitude an d the resonant tf field sets as if in coherency between these energy levels . Such resonances can only be observed when relaxation processes play an es sential role, which permits them to be defined as the relaxation-stimulated resonances. The simplest relaxation model of so-called one-way and localiz ed relaxation is proposed. Within this model an analytical expression for M ossbauer absorption spectra is derived, based on which the specific feature s of the new resonant effects are analysed in detail.