Comparison and Calibration of Fluxgate and SQUID Magnetorelaxometry Techniques for the Characterization of Magnetic Core-Shell Nanoparticles

Magnetorelaxometry can be applied for the comprehensive and fast characterization of magnetic core-shell nanoparticles. The magnetic relaxation of magnetic nanoparticle samples measured with a differential fluxgate-having the potential for a standard testing tool-and a low- T_c SQUID system-acting as a highly sensitive reference system-is compared. It is shown that magnetorelaxation curves agree, i.e., they are not influenced by the different experimental setup. Furthermore, utilizing tiny coils as calibration standards, the measured magnetic flux density can be referred to a magnetic moment of the sample, and measurement data can be quantitatively transferred from one system to the other.