OPM magnetorelaxometry in the presence of a DC bias field
in: EPJ Quantum Technology (2020)
Spatial quantitative information about magnetic nano particle (MNP) distributions is a prerequisite for biomedical applications like magnetic hyperthermia and magnetic drugtargeting. This information can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation of previously aligned MNP’s magnetic moments is measured by sensitive magnetometers and an inverse problem is solved. To remove or minimize the magnetic shielding in which MRX imaging is carried out today, the knowledge of the inﬂuence of background magnetic ﬁelds on the MNP’s relaxation is a prerequisite. We show MRX measurements using an intensity-modulated optically pumped magnetometer (OPM) in background magnetic ﬁelds of up to 100μT. We show that the relaxation parameters alter or maybe intentionally altered signiﬁcantly by applying static ﬁelds parallel or antiparallel to the MNP’s alignment direction. Further, not only the relaxation process of the MNP’s magnetic moments could be measured with OPM, but also their alignment due to the MRX excitation ﬁeld.