Linear dynamics of a magnetic subsystem in a quasi-Ising magnet

Microwave absorption at frequencies from 37 to 85 GHz was studied for a Dy_0.3Y_2.7Fe₅O₁₂ single crystal in pulsed magnetic fields of up to 30 T at T=4.2 K. The magnetic field was aligned with the [100] direction. For the fields above 4 T, several soft magnetic-resonance modes were observed, most of them being caused by the static phase transitions induced by a strong external magnetic field. The field-independent absorption lines away from the points of phase transition may be due to the dynamic Jahn-Teller magnetic effect.