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

TL;DR

This paper presents a compact adiabatic-demagnetization refrigerator designed to fit within a standard SQUID magnetometer, enabling ultra-low temperature measurements with minimal background noise and no complex gas handling.

Contribution

A miniaturized, self-contained T-ADR system compatible with commercial SQUID magnetometers, achieving temperatures below 0.6 K without complex gas systems.

Findings

Achieved lowest temperature of ~0.56 K with the T-ADR.

Can detect magnetization anomalies as small as 1×10⁻⁷ emu.

Background noise level is ~5×10⁻⁵ emu below 2 K at 100 Oe.

Abstract

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.