Development of a Compact Moving-Sample Magnetometer Using High-$T_{\text{c}}$ Superconducting Quantum Interference Device

We developed a compact moving-sample magnetometer that uses a high-temperature superconductor--superconducting quantum interference device (high-$T_{\text{c}}$ SQUID) to directly measure the flux coupled to a normal detection coil from a sample's magnetic moment in the presence of an external DC magnetic field. The moving-sample method is employed by inserting the sample between the poles of a DC electromagnet and vibrating the sample along the axis perpendicular to the external field axis using an actuator at a frequency of 2.693 Hz. First, the magnetic field of the sample is transferred by a first-order differential normal Cu coil to a SQUID for detection. Then, the SQUID output is fed to a lock-in amplifier for detection. The critical feature of the system design is the use of high-$T_{\text{c}}$ SQUID, which enables the realization of a compact system. The basic characteristics of the developed system are presented, and the current system exhibited a detection limit of $1\times 10^{-7}$ emu.