Negative–Positive–Positive Sequential Method for Accurate Hysteresis Loop Measurement of Permanent Magnetic Materials Based on Pulsed Magnetic Field

Pulsed field magnetometer (PFM) can achieve higher magnetic field at a lower cost, suitable for measuring ultrahigh coercive permanent magnets, but it generates eddy currents during the test, which affects the measurement accuracy. To solve this issue, this article proposes a new method for hysteresis loop measurement of permanent magnetic materials that requires only four half-wave pulses, called the negative–positive–positive (NPP) sequential method. According to the NPP method, we employ the difference between magnetic flip and no-flip pulses to eliminate interference signals like eddy currents while retaining the magnetic signal of the permanent magnet. In addition, this study addresses two major issues of the NPP method in magnetic measurement applications: extracting information about the eddy current magnetic field generated by the background magnetic field and by the magnetic polarization field of the sample, respectively, from the measured signals. Experimental results proves that this measurement method can achieve a measurement accuracy within 1% deviation and a test repeatability within 0.25% deviation.