Impedance permeability typically denoted by μ_Z - a type of magnetic permeability which is used to quantify the effectiveness of the given magnetic material in producing useful magnetic flux from a given level of exciting magnetising current, without analysing the specific components of the magnetising currents (e.g. resistive-like for power loss, rather than inductive-like for pure inductive reactance).¹⁾

The definition of impedance permeability is based on measuring the peak magnetic flux density B_peak and RMS value of the applied magnetic field strength H_RMS as the exciting current I_RMS and simplistically assuming that the signal is sinusoidal, so that the scaling is made just by multiplying by √2 in order to obtain the apparent peak value H_peak.²⁾

This type of definition is very convenient in practice, because RMS current is easily measurable by most ammeters (and also RMS voltage can be used to derive B_peak from Faraday's law of induction).

In a general case, the values of permeability calculated with this method will differ by some amount from the amplitude magnetic permeability based on true measured peak values of B and H, especially at higher amplitudes of excitation where the distortions in either B or H cannot be neglected, even when the excitation is set up to be purely sinusoidal. This is because for distorted (non-sinusoidal) waveforms the relationship between peak, average, and RMS values is no longer linear.

• Types of magnetic permeability