Dichroism Program

When materials absorb soft x-rays,* they experience electronic excitations from tightly bound core states to empty, low-energy valence-band states characterized by lattice symmetry, electronic configuration (charge state, orbital occupation), and magnetic order. X-ray absorption depends strongly on the x-ray polarization (linear, circular) and its relative alignment to the local environment or symmetry of the absorbing ion (orientation of magnetic moments, electronic orbitals, crystal directions, etc.). Combining polarization-dependent x-ray absorption spectroscopy, scattering, and imaging allows us to develop a detailed picture of the interplay between atomic, electronic, and magnetic degrees of freedom. Time-resolved dichroism measurements utilize the pulsed structure of the ALS x-ray beam (70 ps x-ray pulses, every 2 ns) and provide unique opportunities to study, for example, magnetization dynamics and the flow of spin currents through multilayered spintronic devices.

Our research includes the intriguing physics of correlated electron systems, prototypical spintronics devices employing the electron spin to store and process digital information, and biomineralization (i.e., magnetic or birefringent materials synthesized by living organisms). We are continuously optimizing our beamlines and endstations—for new fields of study, improved resolution, automation, and ease of use—and developing novel instruments to enable exploration of exciting physical mechanisms underlying functional materials.

* Typical range: 400–2000 eV (or about 0.6–3 nm in wavelength)