Nonlinear response of superfluid 3He fermions to a longitudinal rf magnetic field

The excitation of the A and A1 phases of superfluid 3He by a variable field parallel to a constant field is studied. It is shown that the longitudinal varying magnetic field does not cause a parametric instability in the system since the excitations in 3He are fermions. For small values of time, the magnetization of the system oscillates with the pumping frequency, as well as with a low resonance frequency whose value in the resonance is determined by the amplitude of the varying field. Introduction of the collision relaxation leads to a damping of the low-frequency oscillations. As the amplitude of the pumping field increases, the power absorbed by the system becomes limited.

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