Complex Quantum Systems/Condensed Matter Seminar

Barbara Jones, IBM Almaden Research Center

"First-principles Study of Atomic-Scale Engineered Spin Chains"

3:00pm, RLM 7.114

(Please note special date and room for this seminar.)

Abstract:

First-principles Study of Atomic-Scale Engineered Spin Chains

We have studied the unusual charge and spin properties of magnetic atoms (Mn, Co, Fe, Ti, Gd) on a complex surface as constructed by STM. This surface, a lattice of N atoms on Cu(100), was designed to be insulating in order to inhibit the Kondo effect. However, the magnetic adatom may be drawn down into the surface, or stay high above and attract surface atoms to it, with very different resulting properties. We show illustrations from our electronic structure calculations of these systems. The various magnetic atoms exhibit behavior ranging from spin chains to large-anisotropy atomic-scale molecular magnets to a Kondo effect for Co and Ti. Finally, when two magnetic atoms are close to one another, their magnetic spins can interact, with complex and interesting results. We calculate the behavior of dimers, with an excellent match to experimental values of the exchange coupling. We moreover show that the coupling can be decomposed into three different pairing interactions and how to extract the values of each separately, with unexpected contrasts between two binding sites. I will conclude with some comments about the role of first-principles calculations for nanostructures.