Project

metal-insulator transitions; charge; magnetic and orbtial ordering; metal-insulator transition; orbital order; magnetic order; structural deformations; charge order

Lead
Lay summary
The fundamental understanding of the microscopic origin of metal-insulator transitions is of general importance in oxides. We would like to address the question what happens on the atomic level when conductivity is suppressed, e.g. how get the electrons localized. The fundamental understanding of the microscopic origin of metal-insulator transitions has recently attracted renewed interest, in particular, since the discovery of high-Tc superconductivity and colossal-magnetoresistance in manganites. These materials are oxides which has strange electric and magnetic properties and may are materials for technical applications for the next generation. Here we would like to understand basic questions of what happens on the atomic level to obtain a better understanding of the properties of the materials.Important unresolved questions are; how do the charge carriers become localized? Is this due to charge- and/or orbital-ordering? Is the magnetic ordering connected with the metal-insulator transition, and what is the nature of these orderings? What is the electronic state of the (3d transition) metal ions? With a new technique, soft x-ray resonant scattering (presently available at the Swiss Light Source), we can directly determine the orbital orientation and charge (electron) ordering at the metal-insulator transition, occurring at the different atoms in the crystal lattice. We can combine this with the microscopic information on the atomic magnetic moments and how the atoms are arranged in the material (in a lattice building a crystal, meaning have a periodic arrangement).These measurements have a great potential to resolve the microscopic origin of metal-insulator transitions and correspondingly will help us understand better how electrons correlate and behave in these conductive oxides. Such understanding is important for possible future applications of these materials.

Direct link to Lay Summary

Last update: 21.02.2013

Number	Title	Start	Funding scheme

The fundamental understanding of the microscopic origin of metal-insulator transitions has recently attracted renewed interest, in particular, since the discovery of high-Tc superconductivity and colossal-magnetoresistance in manganites. One of the important unresolved questions is; how do the charge carriers become localized? Is this due to charge- and/or orbital-ordering? Is the magnetic ordering connected with the metal-insulator transition, and what is the nature of these orderings? What is the electronic state of the (3d transition) metal ions? With a new technique, soft x-ray resonant scattering (presently available at the SLS), we can directly determine the orbital (charge) orientation and ordering at the metal-insulator transition. Furthermore, the combination with other techniques, such as x-ray absorption, and non-resonant x-ray scattering, allows us to obtain a clear microscopic picture of the charge, orbital and magnetic ordering associated with the metal-insulator transition, and the influence on the crystal structure. Therefore, these measurements have a great potential to resolve the microscopic origin of metal-insulator transitions. Here we ask for ½ year extension for the PhD project of Miryam García-Fernández for completion of the study.