Collective Mode in a d_(x²-y²) + id_xy Superconductor

We consider a superconducting state with a mixed symmetry order parameter components, e.g. d+is or d+id' with d'= d_{xy}. We argue for the existence of the new orbital magnetization mode which corresponds to the oscillations of relative phase \phi between two components around an equilibrium value of \phi = \pi/2. It is similar to the so called ``clapping'' mode in superfluid 3He-A. We estimate the frequency of this mode \omega_0(B,T) depending on the field and temperature for the specific case of magnetic field induced d'= d_{xy} state. We find that this mode is tunable with an applied magnetic field with \omega_0(B,T) \propto B D_0, where D_0 is the magnitude of the d-wave order parameter. We also estimate the velocity s(B,T) of this mode.