Spin structures in pure and rare earth doped thin ferrites

Electrons in low dimensional systems such as heterostructures, thin films, surfaces and interfaces are at the heart of many interesting phenomena. A contemporary exploitation of charge, spin and orbital degrees of freedom is a promising research field at fundamental and application levels. Of particular interest in this context is magnonics, whose main aim is to study and to explore spin wave propagation in nanomaterials. Non- collinear spin structures, such as magnetic domain walls, can also be exploited to control the amplitude or phase of spin waves. Further functionalities can be achieved by introducing specific magnetic dopants to manipulate electronic and magnetic properties of the host material. In non-centrosymmetric magnetic materials or thin films, a specific doping can induce strong Dzyaloshinskii-Moriya interaction forming topologically protected magnetic objects like skyrmions. The proposal aims to investigate and in particular design the atomic structure and magnetic properties of ultra- thin pristine and doped nickel ferrite films from both perspectives experimentally and theoretically. It is expected that ultra-thin films grown lattice matched on other spinel substrates by either molecular beam epitaxy or by magnetron sputtering exhibit by far a superior crystal quality over bulk samples. We aim to study the effect of doping with rare earth metals and in a second step by introducing electrons into the film to enhance the the Ruderman-Kittel-Kasuya-Yoshida interaction between the rare earth dopants. The goal of this subset of experiments is to harden the magnetic properties (e.g. enhancement of the transition temperature, the coercivity, and remanence) which as a result of the finite sample size are expected to be diminish with respect to a bulk sample.