  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 the diameter $8.5$ mm and the 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 Gd$_3$Ga$_5$O$_{12}$ garnet ($\sim 2$ grams) used
as a magnetic refrigerant, the routinely achievable lowest temperature is $\sim
0.56$ K. The lower detection limit for a magnetization anomaly is $\sim 1
\times 10^{-7}$ emu, estimated from fluctuation of the measured magnetization.
The background level is $\sim 5 \times 10^{-5}$ emu below 2 K at $H = 100$ Oe,
which is largely attributable to a contaminating paramagnetic signal from the
magnetic refrigerant.

Instrumentation and Detectors;Strongly Correlated Electrons;Superconductivity