ISBN 9783843938020

978-3-8439-3802-0, Reihe Physik

Jan Peter Hermenau
Spin-lifetimes of bottom-up construced nanomagnets

195 Seiten, Dissertation Universität Hamburg (2018), Softcover, A5

Zusammenfassung / Abstract

The sensitivity of quantum systems to their closest environment requires specialized architectures of future quantum computing and spintronic devices. Typically, the interaction with the surrounding especially leads to short spin-lifetimes of magnetic systems, which is a constraint for many applications. Hence, the protection of the magnetic moments by decoupling from the environment has been considered to be the most promising approach towards atomic sized devices. However, such a decoupling also restricts the capability to communicate with other building blocks as required for potential future applications.

In order to overcome this drawback, using a contrary approach, this thesis is concerned with the magnetic stability of quantum magnets that are strongly coupled to the underlying substrate. In particular, single iron (Fe) atoms, artificially built Fe clusters of different size and shape as well as complexes of Fe clusters magnetically coupled to single Fe atoms are investigated by means of (spin-polarized) scanning tunnelling microscopy and spectroscopy. In all these systems, the Fe atoms are directly adsorbed on a bare (111) platinum surface, such that the moment bearing orbitals of the Fe atoms are in direct contact with an electrically conducting substrate.

Nonetheless, surprisingly long spin-lifetimes were measured for single Fe atoms, but espacially for atom-by-atom constructed clusters and complexes of individual Fe atoms and a cluster. The strong coupling to the platinum surface not only enables to realize stable magnets consisting of only three Fe atoms but also allows to drive the system into the quantummechanical Kondo regime. Additionally, the RKKY coupling between Fe atoms and cluster within the complexes can be used to transfer information between the two constituents. Remarkably, the transfer of information as well as the overall magnetic stability strongly depends on the symmetry/geometry of the built complex which opens new ways for a possible usage of these kind of structures in future spinelectronic devices.