Critical parameters of nuclear magnon Bose–Einstein condensation in systems with dynamical frequency shift

The critical conditions for the Bose–Einstein condensation of quasi equilibrium nuclear magnons in the easy-plane antiferromagnets CsMnF$_{3}$ and MnCO$_{3}$ are theoretically derived. Both systems possess the dynamical frequency shift, the dependence of the precession frequency on the magnetization deflection angle and one is able to observe the magnetic resonance signals in very non-equilibrium conditions when the frequency of pumping is higher than precession frequency. The frequency difference in this case can be compensated by the increasing of deflection angle.