Large Improvements of Uniformity and Sensitivity From Reshaped Detection Coil for a Magnetometer

The vibrating sample magnetometer is one of the most popular choices for measuring magnetic moment. The detection coil array determines the performance of a vibrating sample magnetometer to a great extent. In the past decades, researches have been striving to finely adjust the dimensions and spatial location of the circular coils to obtain a uniform zone of sensitivity. Here, we found that reshaping the traditional circular coils can be a simple but quite effective solution. Two noncircular coil designs: semicircular and oblong coils were proposed based on the distribution of magnetic flux density variation induced by the vibrating sample on the electromagnet pole plane via finite element analysis. Compared with the conventional circular coils, the proposed semicircular/oblong coils exhibited larger uniform zone by about 18%/20% and significantly enhanced sensitivity by about 47%/49% at the center of the coil array, respectively, under the limited circular area on the pole plane. Furthermore, by appropriately enlarging the semicircular and oblong coils while maintaining the distance between the left and right coil pairs unchanged, a uniform zone expansion of about 53%/35% and a sensitivity increase of about 9%/11% over the circular coils were obtained. The simultaneous improvement in both the uniform zone and sensitivity via detection coil reshaping is advantageous for enhancing the repeatability and accuracy of the vibrating sample magnetometer.