Impedance and Magnetic Permeability of Soft Ferromagnetic Metals

We report on impedance measurements in the Heusler compound Pd2MnSn, Gd metal and the re-entrant alloy Au0.82Fe0.18. Using a computational procedure, the real and imaginary components of the circumferential permeability could be determined from the complex impedance data. We show that the temperature dependence of the permeability is useful to study magnetic phase transitions, whereas valuable information on domain-wall motion and spin rotation processes may be obtained from appropriate analyses of the frequency and external magnetic field dependences of the complex permeability.