specifying effective or initial magnetic permeability of a ferrite rod

[dork_matter]

For a ferrite rod, should I specify the initial magnetic permeability(mu_i) for the given material or the computed effective permeability of the rod (mu_rod) which is based on the finite dimensions of the rod. In my case, mu_i = 2300 and mu_rod = 30.

The Abaqus User's Guide did not provide guidance to this question. Thanks in advance!