US 7,541,805 B2
Magnetic characteristics measuring method and system
Masaki Mito, Kitakyushu (Japan); Kunihiko Irie, Kobe (Japan); Junpei Yamada, Kitakyushu (Japan); Seishi Takagi, Kitakyushu (Japan); and Hiroyuki Deguchi, Kitakyushu (Japan)
Assigned to Kyushu Institute of Technology, Fukuoka (Japan)
Filed on Mar. 29, 2007, as Appl. No. 11/693,476.
Claims priority of application No. 2006-259977 (JP), filed on Sep. 26, 2006.
Prior Publication US 2008/0074110 A1, Mar. 27, 2008
Int. Cl. G01R 33/035 (2006.01); G01N 27/72 (2006.01)
U.S. Cl. 324—248  [324/229] 9 Claims
OG exemplary drawing
 
1. 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.