Zero dead time rotational drift spectroscopy for magnetic particle ensembles

Rotational drift spectroscopy (RDS) aims at measuring the nonlinear rotation of magnetic nanoparticles in suspension in rotating magnetic fields. This drift has been measured on single particles. The first experimental realization was limited by a long dead time of 3 ms between the initial pulse and the actual measurement. The signal decay time after the initial pulse is typically rather short, e.g., 340 μs for magnetic particles with a hydrodynamic diameter of 100 nm if suspended in water. Therefore a dead time of 3 ms severely limits the range of particle systems that can be measured. The presented work suggests a new measurement sequence which reduces the dead time of the measurement by orders of magnitude. Shown are simulation results of the magnetic particle response of the suggested measurement sequence. Previous methods couldn't measure typical magnetic particle suspensions because of its long dead time of 3 ms. The new RDS sequence modification offers a possibility for completely overcome this limitation.