title: A SQUID based AC susceptometer for the investigation of large samples.
abstract: 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.
authors.affiliation: Istituto di Elettronica dello Stato Solido, CNR, Roma, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Pasquarelli
authors.forename: C
authors.initials: C
authors.lastname: Del Gratta
authors.forename: S
authors.initials: S
authors.lastname: Della Penna
authors.forename: S
authors.initials: S
authors.lastname: Di Luzio
authors.forename: V
authors.initials: V
authors.lastname: Pizzella
authors.forename: G L
authors.initials: GL
authors.lastname: Romani
mesh_terms: D006801:Humans; D008280:Magnetics; D008962:Models, Theoretical; D012680:Sensitivity and Specificity; D013672:Technology