A SQUID based AC susceptometer for the investigation of large samples.
We developed a SQUID based susceptometer with a large available magnetized volume for the investigation of large objects. The magnetizing field is generated by a pair of Helmoltz coils. To achieve a high signal-to-noise ratio, the susceptometer is operated in a lock-in mode with an AC magnetizing field. A negative feedback control allows the rejection of the applied field with a relative residual of 1 x 10(-7). The apparatus was tested with substances of known magnetic susceptibility. The overall sensitivity, stated in terms of the magnetic moment, is better than 7 x 10(-11) A m2 for small samples.
Pasquarelli
A
A
Istituto di Elettronica dello Stato Solido, CNR, Roma, Italy.
Del Gratta
C
C
Della Penna
S
S
Di Luzio
S
S
Pizzella
V
V
Romani
G L
GL
D006801:Humans; D008280:Magnetics; D008962:Models, Theoretical; D012680:Sensitivity and Specificity; D013672:Technology