Crackling noise microscopy.

Crackling noise is a scale-invariant phenomenon found in various driven nonlinear dynamical material systems as a response to external stimuli such as force or external fields. Jerky material movements in the form of avalanches can span many orders of magnitude in size and follow universal scaling rules described by power laws. The concept was originally studied as Barkhausen noise in magnetic materials and now is used in diverse fields from earthquake research and building materials monitoring to fundamental research involving phase transitions and neural networks.

Enhanced Room Temperature Ferromagnetism in Highly Strained 2D Semiconductor CrGeTe.

Emergent magnetism in van der Waals materials offers exciting opportunities in fabricating atomically thin spintronic devices. One pertinent obstacle has been the low transition temperatures () inherent to these materials, precluding room temperature applications. Here, we show that large structural gradients found in highly strained nanoscale wrinkles in CrGeTe (CGT) lead to significant increases of .

Detection of Topological Spin Textures via Nonlinear Magnetic Responses.

Topologically nontrivial spin textures, such as skyrmions and dislocations, display emergent electrodynamics and can be moved by spin currents over macroscopic distances. These unique properties and their nanoscale size make them excellent candidates for the development of next-generation race-track memory and unconventional computing. A major challenge for these applications and the investigation of nanoscale magnetic structures in general is the realization of suitable detection schemes.

Dislocation-Driven Relaxation Processes at the Conical to Helical Phase Transition in FeGe.

The formation of topological spin textures at the nanoscale has a significant impact on the long-range order and dynamical response of magnetic materials. We study the relaxation mechanisms at the conical-to-helical phase transition in the chiral magnet FeGe. By combining macroscopic ac susceptibility measurement, surface-sensitive magnetic force microscopy, and micromagnetic simulations, we demonstrate how the motion of magnetic topological defects, here edge dislocations, impacts the local formation of a stable helimagnetic spin structure.

In-depth atomic force microscopy investigation of nanoscale mechanical properties of Pāua nacre.

Over millions of years, nature has created complex hierarchical structures with exceptional mechanical properties. The nacre of various seashells is an example of such structures, which is formed out of a mainly inorganic mineral with organic material inclusions in a layered arrangement. Due to its high impact-resisting mechanical properties, these structures have been widely investigated and mimicked in artificial nacre-type composite materials.

Anisotropic Ion Migration and Electronic Conduction in van der Waals Ferroelectric CuInPS.

Van der Waals (vdW) thio- and seleno-phosphates have recently gained considerable attention for the use as "active" dielectrics in two-dimensional/quasi-two-dimensional electronic devices. Bulk ionic conductivity in these materials has been identified as a key factor for the control of their electronic properties. However, direct evidence of specific ion species' migration at the nanoscale, particularly under electric fields, and its impact on material properties has been elusive.

Functional Ferroic Domain Walls for Nanoelectronics.

A prominent challenge towards novel nanoelectronic technologies is to understand and control materials functionalities down to the smallest scale. Topological defects in ordered solid-state (multi-)ferroic materials, e.g.

Observation of Uncompensated Bound Charges at Improper Ferroelectric Domain Walls.

Low-temperature electrostatic force microscopy (EFM) is used to probe unconventional domain walls in the improper ferroelectric semiconductor ErCaMnO down to cryogenic temperatures. The low-temperature EFM maps reveal pronounced electric far fields generated by partially uncompensated domain-wall bound charges. Positively and negatively charged walls display qualitatively different fields as a function of temperature, which we explain based on different screening mechanisms and the corresponding relaxation time of the mobile carriers.

Magnetoelectric Force Microscopy on Antiferromagnetic 180 Domains in Cr₂O₃.

Magnetoelectric force microscopy (MeFM) is characterized as methodical tool for the investigation of antiferromagnetic domain states, in particular of the 180 ∘ variety. As reference compound for this investigation we use Cr 2 O 3 . Access to the antiferromagnetic order is provided by the linear magnetoelectric effect.