JANUS DYNAMICS · Magnetization dynamics in anisotropic magnetic nanoparticles investigated using time-resolved X-ray and neutron scattering techniques

The magnetization relaxation of nanosized magnetic objects plays an important role for their technological applicability. For applications in data storage, a large magnetic anisotropy is required in order to retain the magnetization state in the required relaxation time and temperature range. For application in the fields of magnetic imaging or magnetic hyperthermia, however, the electromagnetically induced relaxation of superparamagnetic nanoparticles is desired. Magnetization relaxation effects depend on the interplay of magnetic anisotropy and volume and are thus largely influenced by the nanoparticle composition, shape, interface effects, and interparticle interactions.In this project, we will quantitatively investigate the magnetization relaxation of magnetic nanoparticles and their assemblies. In particular, the effects of shape anisotropy, exchange bias, and magnetoelectric coupling in anisotropic nanoparticles will be explored. Janus nanoparticles, consisting of two epitaxially aligned hemispheres of different composition, allow for a controlled variation of anisotropic shape and interface effects in nanoparticles, and thus represent suitable model systems for the proposed study. Particular emphasis will be given to multifunctional Janus particles, combining e.g. magnetism and polarity with low dimensionality, which may potentially serve as building blocks for multifunctional nanomaterials. We will investigate the magnetization relaxation effects by application of advanced X-ray and neutron scattering techniques including stroboscopic small-angle scattering and nuclear resonant X-ray scattering.As a result, we expect to gain precise information on the influence of exchange bias, magnetoelectric coupling, and interparticle interactions on the Néel relaxation. This will improve the understanding of magnetization dynamics in anisotropic nanoparticles and may thus contribute to the exploration of further suitable nanomaterials for technological applications.""