High sensitivity direct magnetic field detection based metrology for ultra-thin magnetic films and Li-ion cells.

Ultra-low magnetic field sensing is emerging as a tool for materials' diagnostics, particularly for the operando studies of electrochemical systems. A magnetic metrology system having the capability of sensing fields as low as ∼1.88 pT has been setup for such studies using a commercial atomic magnetometer. The magnetometer setup is isolated from environmental perturbations, such as mechanical vibrations, electrical noises, and ambient magnetic fields, in order to measure small signals from the samples under study. Magnetic field measurements on ferromagnetic (permalloy, Ni0.8Fe0.2) thin films, monolayers of MoS2, vanadium doped MoS2, and lithium electro-deposited copper electrodes are performed to demonstrate the sensitivity of the setup. Magnetic field scanning of commercial Li-ion cells has also been performed using this magnetic metrology method, indicating the scope of the setup for operando diagnostics.