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Seminar | X-Ray Science Division

Imaging Ultrafast and Ultrasmall: Unraveling Magnetic and Electronic Behavior Using Time-resolved Coherent X-ray Scattering

APS Ultrafast Interest Group

Abstract: Ultrafast laser control of magnetic and correlated materials has emerged as a fascinating avenue of manipulating magnetic and electronic behavior at femtosecond to picosecond timescales. Ultrafast manipulation of these materials has also been envisioned as a new paradigm for next generation memory and data storage devices. Numerous studies have been performed for both magnetic metallic systems as well as complex oxides to understand the mechanism underlying laser excitation. However, it has been recently recognized that spatial domain structure and nanoscale heterogeneities can play a critical role in dictating ultrafast behavior. 

In this talk, I will focus on utilizing time-resolved x-ray scattering and nanodiffraction studies to study spatial texture dependent dynamics in magnetic multilayers and correlated systems. I will describe our recent experimental studies using emerging synchrotron techniques and free electron laser such as FERMI. In magnetic multilayers, we uncover a symmetry-dependent behavior of the ultrafast response. Labyrinth domain structure with no translation symmetry exhibit an ultrafast shift in their isotropic diffraction peak position that indicates their spatial rearrangement. On the other hand, anisotropic domains with translation symmetry do not exhibit any modification of their anisotropic diffraction peak position. I will also show spatially dependent ultrafast response measured at APS for complex oxides such as rare-earth nickelates. These intriguing observations suggest preferential, texture-dependent paths not only for the transport of angular momentum, but also for structural rearrangements. These measurements provide us with a unique way to study and manipulate spin, charge and lattice degrees of freedom.

Bio: Roopali Kukreja is a Professor of Materials Science and Engineering at UC Davis. Her research group focuses on understanding ultrafast dynamics of quantum materials for applications in energy-efficient computing devices. The main focus is on manipulating quantum materials using external stimuli such as laser pulses, electric field, epitaxial strain and temperature.