A new MIEZE technique for investigating relaxation of magnetic nanoparticles

There is no reduction in the contrast of a modulated intensity of zero effort (MIEZE) signal even when magnetic scattering occurs, whereas the contrasts of neutron spin echo and neutron resonance spin echo are reduced by more than a factor of two. However, since MIEZE measures both the intensities of quasielastic nuclear and magnetic scatterings, it is generally not easy to use a conventional MIEZE setup to simultaneously separate magnetic and nonmagnetic fluctuations of magnetic nanoscale particles. We propose a new MIEZE technique, which involves inserting a second analyzer and an additional π-flipper that is able to distinguish between the magnetic and nonmagnetic quasielastic scattering intensities. We succeeded in observing superparamagnetic fluctuations of magnetite particles in a ferrofluid by using this new technique.