$\mu_{p}$ (also μp or mu p)¹⁾ - it is a value of the real part of the complex magnetic permeability measured at low excitation (e.g. 40 G or 4 mT) hence equivalent to initial magnetic permeability.

The value of $\mu_{p}$ is measured with impedance meter considering the parallel model of impedance, in which the active and reactive parts are connected in parallel.²⁾

• Magnetic permeability