A Static-Sample Magnetometer for Characterizing Weak Magnetic Materials

In this article, a static-sample magnetometer is presented to measure the relative permeability of weakly magnetic materials. The method consists of scanning the magnetic field inside a dipole magnet by using an NMR teslameter to measure the perturbation of a test specimen on the externally applied field. Then, an inverse problem is used to compute the specimen’s relative permeability. As a case study, the measurement of three different materials with different shapes and dimensions is carried out. The method was validated by measuring the same material by vibrating sample magnetometry as proposed by the standard ASTM A342/A342M-14. The expanded measurement uncertainty of the relative permeability, evaluated by Monte Carlo simulations, is about $10^{-4}$ for all the cases, with a level of confidence of 95%.