Magnetism of Nano- to Micrometer-Sized Anisotropic Materials

Magnetic materials have a large variety of everyday uses. From audio speakers to magnetic memory or logic devices, many branches or modern technology at least partially rely on magnets. Magnetometry of individual nano- to micron-sized magnetic particles using conventional, commercially available measurement techniques is complicated due to the inherently small generated signals and hence the necessity to investigate large ensembles of particles. This typically leads to random orientation of, and considerable interactions between the particles.
Consequently, information on magnetic states or anisotropies is averaged out. Dynamic Cantilever Magnetometry (DCM) has been established as a sensitive method to investigate very small, individual magnets without the need for electrical contacts or large sample volumes. This thesis offers a contribution to the research on the magnetism of nano- to micrometersized magnetic particles using Dynamic Cantilever Magnetometry. We analyze the data using analytical models and micromagnetic simulations. We demonstrate the manipulation of the remanent state of spherical Janus Particles with a magnetic cap, using exchange bias as a means to provide an artificial, unidirectional anisotropy. We further analyze the anisotropy and blocking temperature of superparamagnetic maghemite mesocrystals. Both types of magnetic systems have previously not been investigated on the individual level. We also highlight the contribution to the investigation of phase transitions and domain wall magnetism in the
multiferroic polar magnet GaV4Se8.