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John W. Freeland at BESSY II virtual seminar

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On November 24th, PDI guest scientist John W. Freeland will speak at the virtual seminar at BESSY II, the 240 meter storage ring in Berlin-Adlershof. John is visiting from Argonne National Laboratory where he focuses his research on the application of polarized X-ray techniques to probe the magnetism of surfaces and interfaces. John has been visiting PDI since summer this year, working with Roman Engel-Herbert, Johanna Nordlander, and Vladimir Kaganer on X-ray diffraction and the PHARAO beamline at BESSY II.

BESSY II is a third generation storage ring that has been in operation since 1999 and provides ultrabright photon beams from the long wavelength Terahertz region to hard X-rays with complete control of the energy range and the polarization of the radiation. The facility is operated by the Helmholtz-Zentrum Berlin. The PDI team is responsible for the operation of the PHARAO beamline, which is used to observe in-situ growth during molecular beam epitaxy by means of diffraction experiments. The beamline is equipped with a heavy-duty goniometer, on which a custom-designed MBE system is mounted. More information about BESSY II is available in German here.

Talk title: Exploring Dynamics of Electronic and Magnetic Order with Ultrafast X-rays

Quantum materials are a unique platform that host a variety of emergent states due to the strong interaction between the structural, electronic, and magnetic degrees of freedom. With the ability to grown high-quality thin films opens the door to add dimensionality and interactions across interfaces of materials with dissimilar order. Understanding the properties can be quite challenging given the small sample volumes and mixture of many elements. Through the use of X-ray spectroscopy and scattering, one can separate the role of these degrees of freedom to gain a deeper understanding. This talk will focus on exploring the how the degrees of freedom interact using ultrafast synchrotron and free electron laser probes. Examples will include magnetic topologoical insulators and the insulating antiferromagnetic NdNiO3.1,2

1 Stoica, V. A. et al. Magnetic order driven ultrafast phase transition in NdNiO3. Phys Rev B 106, 165104 (2022).
2 Padmanabhan, H. et al. Large Exchange Coupling Between Localized Spins and Topological Bands in MnBi2Te4. Adv. Mater. 34, 2202841 (2022).

Join the virtual seminar

November 24th, 14:30 | Zoom link