Problem to eddy current response in 2D modeling

I built a model in COMSOL 4.3a using AC/DC module to simulate eddy current response excited by a linear coil. A sin wave is used as excitation signal in a linear coil, and the response of eddy current density under the coil has distortion in amplitude and frequency of sin waves.

For single frequency, the response should be the same frequency as excitation. Is there any problems in my set-up? Thanks a lot!

Please find the model and signals for excitation and eddy current density attached.