Seminars Archive

High pressure studies using x-ray absorption spectroscopy and synchrotron radiation

Abstract
High pressure studies currently enjoy an increasing popularity in different fields covering physical, chemical, earth, and life sciences. Pressure may vary considerably the interatomic distances without altering the chemical composition or thermal energy of a system, and thus provides an effective means of examining the relationship between structure and properties, leading towards a better fundamental understanding of the underlying phenomena, and for the improved design of applied materials. X-ray absorption spectroscopy (XAS) offers the ability to obtain atom specific information concerning the evolution of the electronic and local structure of matter under different thermodynamic conditions. Additionally, the possibility of measuring spin dependent absorption spectra (XMCD) by using circularly polarized x-rays opens new opportunities to correlate magnetic properties with the electronic and local structure. In this talk, I will present my research activities at the ESRF XAS beamlines through two experiments recently undertaken: (1) to investigate the occurrence of pressure-induced liquid¬liquid phase transitions in molten Sn; (2) to extend the feasibility of high pressure XMCD studies to the low temperature regime, with the first results revealing a pressure induced collapse of strong ferromagnetism in YCo5. Although very diverse, these two examples have been chosen to demonstrate how we can exploit the different abilities of the XAS technique, and how the pressure parameter may be coupled with different non-ambient temperature conditions in synchrotron experiments.