Systematic investigation and correction of the magnetic hysteresis obtained by vibrating sample magnetometry

Abstract

This work focused on a systematic study of data corrections for the vibrating sample magnetometry (VSM) to obtain reliable magnetic properties of strong ferromagnets. We designed the systematic experiments by varying the length-to-radius ratio of VSM samples between 1-5 and provided the step-by-step corrections of two commercial NdFeB powder magnets with reported energy product ((BH)max ) of 6.0±0.5 and 12.7±0.5 MGOe. Without data corrections, the measured hysteresis loops yield the (BH)max between 47.3% and 62.6% of their reported values with improper values of saturation magnetization (Ms ), remnant magnetization (Mr ), and Mr/Ms ratio. To correct the measured VSM hysteresis loop, firstly, the paramagnetic-like slope of 0.0500–0.0735 G/Oe was subtracted until the flat at high fields was obtained. Then, up to 6% of magnetization value and demagnetizing factor (N) of 0.30-0.53 was applied to achieve similar hysteresis loops for all samples. The corrected (BH)max after all processes is around 86-95% of the reported value. Moreover, by examining the samples with different packing densities, it was found that the loose-packed samples exhibit hysteresis distortion, which could be caused by an unwanted magnetostatic interaction and degree of particle rotation of the powder.