Interaction of two magnetic resonance modes in polar phase of superfluid $^3$He

We report results of low frequency nuclear magnetic resonance (NMR) experiments in the superfluid polar phase of $^3$He which is stabilized by a new type of “nematic” aerogel – nafen. We have found that an interaction between transverse and longitudinal NMR modes may essentially influence the spin dynamics. Theoretical formulas for NMR resonant frequencies are derived and applied for interpretation of the experimental results.