Automated and versatile SQUID magnetometer for the measurement of materials properties at millikelvin temperatures

We present the design and construction of a SQUID-based magnetometer for operation down to temperatures T≃10mK, while retaining the compatibility with the sample holders typically used in commercial SQUID magnetometers. The system is based on a dc-SQUID coupled to a second-order gradiometer. The sample is placed inside the plastic mixing chamber of a dilution refrigerator and is thermalized directly by the He3 flow. To measure the magnetic moment, the sample is moved through the gradiometer coils by lifting the whole dilution refrigerator insert. A home-developed software provides full automation and an easy user interface.