Argonne National Laboratory

Ferroic and Ionic Materials

Demonstration of a spin-wave multiplexer.  Spin-wave propagation is controlled by local magnetic fields and detected with spatially resolved inelastic light scattering.  Adapted from K. Vogt et al., Nature Comm. 5, 3727 (2014).

Demonstration of a spin-wave multiplexer. Spin-wave propagation is controlled by local magnetic fields and detected with spatially resolved inelastic light scattering. Adapted from K. Vogt et al., Nature Comm. 5, 3727 (2014).

Our main goal is to obtain new insight into the fundamental physics controlling magnetic, ferroelectric and ionic phenomena by creating new materials and systematically exploring their behavior. By doing so, we can understand the ultimate limits of miniaturization and prepare novel materials with specifically designed functionalities.

The new phenomena that arise through manipulation of spin states push the boundaries of fundamental understanding of nanostructured magnetic materials and underlie novel applications ranging from information technologies to energy conversion. For these reasons, we explore the emergent behavior that arises in structures that integrate ferromagnets, antiferromagnets, superconductors, ferroelectrics and insulators.

In magnetic materials, we tailor properties in metallic and oxide magnetic materials by systematically controlling synthesis conditions, using thin film heterostructures and bulk materials. We use advanced patterning and templating techniques to develop novel spin structures with non-trivial topologies such as skyrmions and artificial spin ices.

Similarly, in ferroelectric and ionic materials, we seek to understand how the energy landscape at the nanoscale can be influenced through geometric patterning or confinement, defect control, and through interfacial interactions. For ferroelectrics, we aim to explore the formation of novel distributions of charge and control the stable topological structures in nanoscale flux-closure and metastable domains.

A particular focus is the use of three-dimensional analysis and imaging techniques that we have developed to visualize domains and their interaction with screening charges in nanostructures as a function of external stimuli such as applied fields, temperature and time.

In recent years, it has become clear that many of the remarkable properties discovered in the field of complex oxide heterostructures may be related to charged defects and their behavior at interfaces. Such phenomena, however, remain poorly understood due to the inherent difficulties in probing defect-interface interactions at the atomic-level and in the environments relevant to defect evolution.

In ionic materials, such as complex oxides, their physical properties are closely related to their defect structures. We investigate this issue by growing heterostructures with precise cation ordering and variable oxygen concentrations, enabling the systematic investigation of defect formation and migration behavior through a combined in situ X-ray / computational theory approach both during synthesis and while processing in different electrochemical environments.