Reducing systematic errors in measurements made by a SQUID magnetometer

A simple method is described which reduces those systematic errors of a superconducting quantum interference device (SQUID) magnetometer that arise from possible radial displacements of the sample in the second-order gradiometer superconducting pickup coil. By rotating the sample rod (and hence the sample) around its axis into a position where the best fit is obtained to the output voltage of the SQUID as the sample is moved through the pickup coil, the accuracy of measuring magnetic moments can be increased significantly. In the cases of an examined Co1.9Fe1.1Si Heusler alloy, pure iron and nickel samples, the accuracy could be increased over the value given in the specification of the device. The suggested method is only meaningful if the measurement uncertainty is dominated by systematic errors – radial displacement in particular – and not by instrumental or environmental noise. •A simple method is described which reduces systematic errors of a SQUID.•The errors arise from a radial displacement of the sample in the gradiometer coil.•The procedure is to rotate the sample rod (with the sample) around its axis.•The best fit to the SQUID voltage has to be attained moving the sample through the coil.•The accuracy of measuring magnetic moment can be increased significantly.