Recoil Permeability, μrec: when exerting a small scale of cyclic magnetic field with positive and reverse direction, ±ΔH, on ferromagnetic
material under some constant external magnetic field, it will cause the variation of the magnetic flux density. μrec is defined by △B and △H according to the following formula. It reflects the stability of magnetization status inside the magnetic material under the influence of external magnetic field.
