SQUID and Hall Effect Magnetometers for Detecting and Characterizing Nanoparticles Used in Biomedical Applications

We reviewed magnetometers built in our group to detect and characterize nanoparticles used in biomedical applications. The SQUID magnetometer was based on a custom-made bulk rf-SQUID and a magnetizing coil. We measure sample magnetic moments using a thermoremanent magnetization technique by applying a magnetic field while lowering the temperature of the nanoparticles below their blocking temperature. Commercial nanoparticles routinely used in magnetic immunoassays were tested. The limit of sensitivity of our SQUID system was estimated to be 10−14 A m2. In addition, we built modular Hall effect magnetometers to characterize custom-made nanoparticles covered with a polymer able to function as a drug carrier. The influence of the coating in the magnetic core was studied. We acquired magnetization curves from room temperature down to 10 K. Zero-field cooling and field cooling curves were obtained as well. The magnetometers built were compared successfully to commercial stand-alone equipment. Finally, we presented a simple magnetometer developed to be used in a classroom laboratory in order to measure the saturation, remanence, and coercive fields of iron oxide microparticles.