This calculator finds complex permeabily at arbitrary frequencies by cubic spline interpolation from tables of values at given frequencies.
An alternate list of frequencies can be entered in the above form as a comma delimited list. Frequencies outside of the range of source data frequencies (ie extrapolations) will not be reported.
Data is derived from manufacturer's published curves for tables where possible, some materials are from my own measurement. The Fair-rite data is from their published CSV files, and note that some contain -ve values for µ' in some cases (eg #75), and these would on the surface appear invalid... so compare calculated results with published permeability curves to ensure that they are sane. The calculator tries to obtain the complex permeability, and if one component is not reliable, it doesn't try to estimate the other.
Note that Amidon sources ferrite from various manufacturers, and it is naive to think that for instance, their 43 material is sourced from Fair-rite or that the Fair-rite permability characteristics apply. At 30/06/2021 the datasheet for Amidon 43 appears to be that of National Magnetics Group H material.