Patent ID: 7541805

Claim:
A method for measuring magnetic characteristics of a sample by use of a superconducting quantum interference device which detects a magnetization of the sample located in the vicinity of a superconducting pickup coil and outputs an electrical signal representing the magnetization, and a coil connected to an AC power supply so as to generate an alternating magnetic field around the superconducting pickup coil, the method comprising the steps of: sampling an AC signal output from the superconducting quantum interference device by use of an A/D converter which is operable in an audio frequency range and outputs a digital signal corresponding to the AC signal; performing phase adjustment so as to optimally correct a time shift of the digital signal in relation to a reference voltage signal; subjecting the phase-adjusted signal to Fourier transformation processing so as to detect harmonic components as magnetic characteristics; and performing harmonic analysis so as to individually extract the rms value of each harmonic component calculated by the Fourier transformation and convert the same to an absolute value.