Speaker
Description
Traditionally, neutron scattering has been the main technique to study spin order and excitations, such antiferromagnetism of LiErF4 [1]. However, exceptional improvements in terms of brilliance of accelerator-based X-ray sources have elevated X-ray scattering as an effective complementary technique that enables elemental sensitivity via electronic resonance effects, as well as the ability to probe small sample volumes.
Reaching sub-Kelvin temperatures at synchrotron X-ray sources is prohibitively difficult due the heat load on the sample from the incident continuous photon beam. This effectively precludes measurements at milli-Kelvin temperatures – hence we turned to pulsed X-ray FELs.
Here we report on the recently commissioned ultralow-temperature vector magnet setup that has recently become available to the user community at the SwissFEL Cristallina-Quantum endstation. We have used single X-ray FEL pulses for resonant magnetic X-ray scattering at the Er L3-edge (8.35 keV), showing that antiferromagnetic order of LiErF4 can be detected at sample temperatures as low as T = 35 mK before the onset of heating. Magnetism can also be tuned via vector magnetic fields, e.g. to lift the degeneracy of magnetic domains, and the effect on the magnetic order parameter directly monitored via the X-ray signal.
This proof-of-principle demonstration of electronic diffraction-before-destruction highlights the advantage of a brilliant, ultrafast X-ray source to measure fragile electron many-body states in the quantum criticality regime.
[1] C. Kraemer et al., Science, 336, 1416 (2012)
| Scientific Topics | Quantum Science |
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