Key Metrics and Experimental Test Bench for Assessing Highly Sensitive Magnetometers in Research

Ultralow magnetic field sensing is rapidly emerging as a technology in various applications, providing a noninvasive and instantaneous method of data acquisition (DAQ). The increasing availability of improved or innovative types of magnetometers promotes the need for a benchmark metric. This contribution focuses on the evaluation of single magnetometer devices that detect magnetic fields in the femtotesla range and are usually used in a magnetically shielded environment. For assessment, a device alignment actuator system is presented that enables an accurate 3-D alignment of the device under test (DuT) around a single point within a known, homogeneous magnetic test field inside the highly magnetically shielded room (MSR), called BMSR-2.1 at the Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany. The defined benchmark metric includes several key parameters, such as frequency response, amplitude stability, frequency stability, and directivity, to name just a few. These parameters are introduced by using different commercial state-of-the-art spin exchange relaxation-free optically pumped magnetometers (SERF-OPMs) and compared to the reference system based on superconducting quantum interference devices (SQUIDs), which remain the gold standard in magnetometry. This approach ensures consistent evaluation across different magnetometer types, provided that they operate at room temperature and fit within the evaluation platform. The platform can also be adapted for multichannel magnetometer systems.