Thin films and nanostructures

Prof. Dr. Michael Huth

Goethe University, Frankfurt am Main

Nanomagnetism

SEM image of nano-tree array
Fig. 1: 2×2 array of Fe-Co nano-trees with non-magnetic segment where the stem and branches join. The non-magnetic part is made of nano-granular Pt.

Nanomagnetic structures are ubiquitous, as they form the basic functional elements in various applications, such as in magnetic storage and information processing, magnonics and spintronics.

In magnetic information storage and processing,the advantages of extending the typically 2D structures into the third dimension for higher integration density have already been realized and have led to developments, such as the racetrack memory. More generally, the importance of gaining a better understanding of magnetic interactions via stray-field couplings has led to the development of artificial spin ice systems.

In artificial spin ice systems the actual limitation to lithographically defined 2D arrays of interacting ferromagnetic nano-islands prevents investigations of novel phases that can emerge from the more complex ground states of frustrated lattices in 3D.

Standard electron lithography techniques are intrinsically designed for 2D pattern formation and, consequently, they are barely suitable for the fabrication of free-form 3D nanostructures. Focused electron beam induced deposition follows a different approach to overcome this EBL-related limitation

Example for micromagnetic calculation
Fig. 2: Example of result of micromagnetic calculation of magnetization distribution in an Fe-Co nano-tree.
We use FEBID to fabricate free-form 3D magnetic nano-architectures, as exemplarily shown in Fig.2. In collaboration with Prof. Jens Müller we study the magnetic properties of these structure by micro-Hall magnetometry. With the help of micromagnetic simulations we are able to explain the observed complex switching behavior.