Absolute calibration of low- and high-field magnetic susceptibilities using rare earth oxides

Abstract

Low- or high-field magnetic susceptibility measurements have been routinely utilized in or even beyond paleomagnetism and environmental magnetism. Susceptibility meters, such as Bartington or Kappabridge, are now commercially available and have enabled us to measure a variety of samples readily. However, interlaboratory or interinstrument calibration is not yet faithfully performed on absolute or even relative scales. The reason is that no standard material is generally accepted for susceptibility calibration. Gadolinium or other rare earth oxides are considered as ideal standard materials because of the high chemical stability. We defined reference susceptibility values for all available paramagnetic rare earth oxides after carefully examining the Landolt-Bornstein database and selected four compounds Nd2O3, Gd2O3, Dy2O3 and Er2O3 as standard materials. We carried out calibration measurements using Bartington and Kappabridge susceptibility meters, a Magnetic Property Measurement System (Quantum Design) and a Vibrating Sample Magnetometer (Princeton Measurements Corporation). Linear relationships between measured and reference values were observed for all the instruments. In some cases, however, measured values deviated significantly from expected values, suggesting that calibration is indeed necessary. If any instrument is calibrated with these rare earth oxides, we can reliably compare absolute susceptibility values measured with any kind of instrument in different laboratories.