Precise magnetization measurements down to 500 mK using a miniature He-3 cryostat and a closed-cycle He-3 gas handling system installed in a SQUID magnetometer without continuous-cooling functionality

We have conducted precise magnetization measurements down to 0.5 K with a miniature He-3 cryostat and a closed-cycle He-3 gas handling system (GHS) for a superconducting quantum interference device magnetometer. The GHS contains two sorption pumps filled with granular charcoals. We pressurize He-3 gas up to ambient pressure for the liquification at 3 K and then pump the vapor for cooling. The lowest sample temperature is similar to 0.5 K and it can persist for 34 h. We demonstrate the performance of the system by observing the Meissner effect of aluminum below the superconducting transition temperature similar to 1 K. We also measured the magnetization curve of the heavy-fermion superconductor CeCoIn5 resulting in successful observation of the lower critical field at 0.5 K.