Getting the reflection coeffcients of Ni-Zn ferrites

I am a begginer user of HFSS and I am simulating the reflection coefficients of diferent kinds of Ni-Zn ferrites at different thicknesses. The datasheet of the manufacturer include the plots of the permeability spectra. I am interested in the range 100MHz-1GHz. The problem is:

How to introduce the complex permeability points in the new definition material setup?

I have seen that I can introduce the points for the realative permeability but these point can not be complex, so how can I do it?

I will apreciate a lot any help you can give me