The seminar is generously funded and organised by the Wilhelm und Else Heraeus Stiftung and will be held in the Physikzentrum in Bad Honnef near Bonn/Germany.
In our everyday life, we are surrounded by electronic devices designed in a way to meet requirements for a certain application, which is determined primarily by their shape, size and rigidity of a substrate. In this respect, the natural question, which surprisingly has only recently been raised, is can one create non-rigid electronics that can be reshaped on demand after its fabrication? The crucial aspect of this technology is the exploitation of flexible ultra-thin membranes in multi-functional devices directly integrable on-chip with currently available main-stream technologies. Until recently, the main focus was on the fabrication of shapeable high-speed electronics and optoelectronics (Figure 1). However, the family of shapeable electronics is not limited to these two members: shapeability enables new directions in photonics, thermoelectrics, and integration with magnetic and ferroic materials. Very recently, a new member was added to this family - the shapeable magnetoelectronics on ultra-thin curved membranes.
Figure 1: Family of shapeable electronics: (Top panel) Opto-electronics: array of light emitting diodes (LEDs). (Bottom left) Electronics: Multifunctional inflatable balloon catheters. (Bottom right) New member of the family – shapeable magneto-electronics: giant magneto-resistive (GMR) sensor element on a free-standing rubber membrane. Shapeability of the magnetic sensor element is due to wrinkle formation.
The boost of progress in the fabrication of those shapeable magnetic nanomembranes has triggered the interest in fundamental aspects of magnetism in curved geometries. For instance, quantum geometrical effects can cause intriguing phenomena such as bound states and topological bandgaps in curved architectures. Magnetoelectronic properties are even more prone to curvature effects because of the interplay among geometrical properties and the magnetic length of externally applied fields. Complex magnetic patterns can be realized relying on a continuous distribution of the macroscopic magnetic moment, which is prepared by shaping magnetic nanomembranes using micro- and nano-fabrication techniques. It is therefore conceivable that magnetic patterns which are at the heart of multiferroicity can be fabricated on demand. From a theoretical point of view, radial magnetized architectures like Swiss roll structures lack inversion- as well as time-reversal symmetry and are therefore characterized by a ferro-toroidic order. The induction of a finite toroidal moment by nanofabrication techniques could lead to new insights on this elusive type of long-range order and its intimately role in mutiferroic behavior.
Figure 2: Magnetic micro-helix coils with unique magnetic configurations: (a) hollow-bar-magnetized, (b) corkscrew-magnetized and (c) radial-magnetized. Radial-magnetized coil (panel (c)) does not exist in nature