Calculated demagnetization curves agree well with the initial remnant magnetization curve. A simple analytical expression was obtained from the curve by fitting the measured initial remnant magnetization data. Anhysteretic demagnetization was performed by applying an alternating step-ramped magnetic field sequence and the vertical dc bias field, simultaneously. The influence of the vertical bias magnetic field on anhysteretic demagnetization was prominent when the amplitude of the alternating magnetic pulse was large enough to saturate the magnetization of the object. The magnetic field due to the vertical remnant magnetization could be estimated by Langevin function with parameters of and .