Tiny adiabatic-demagnetization refrigerator for a commercial superconducting quantum interference device magnetometer

A tiny adiabatic-demagnetization refrigerator (T-ADR) has been developed for a commercial superconducting quantum interference device magnetometer [ Magnetic Property Measurement System (MPMS) from Quantum Design]. The whole T-ADR system is fit in a cylindrical space of diameter 8.5 mm and length 250 mm, and can be inserted into the narrow sample tube of MPMS. A sorption pump is self-contained in T-ADR, and hence no complex gas handling system is necessary. With the single crystalline Gd3Ga5O12 garnet (similar to 2 g) used as a magnetic refrigerant, the routinely achievable lowest temperature is similar to 0.56 K. The lower detection limit for a magnetization anomaly is similar to 1 x 10(-7) emu, estimated from fluctuation of the measured magnetization. The background level is similar to 5 x 10(-5) emu below 2 K at H = 100 Oe, which is largely attributable to a contaminating paramagnetic signal from the magnetic refrigerant. Published by AIP Publishing.