Spin and Exchange Coupling for Ti Embedded in a Surface Dipolar Network

Pushpa Raghani, Boise State University
Jesus Cruz, Georgetown University
Barbara Jones, IBM, Almaden Research Center

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This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Physical Review B, published by American Physical Society. Copyright restrictions may apply. DOI: 10.1103/PhysRevB.84.075422

Abstract

We have studied the spin and exchange coupling of Ti atoms deposited on a Cu2N/Cu(100) surface using density functional theory with generalized gradient approximation +U. In agreement with experiments, we find that Ti has the highest binding on top of Cu atoms. We also find that the spin of individual Ti atoms deposited on the Cu2N/Cu(100) surface increases as Ti coverage on the surface is decreased. For U=0, the spin of a Ti atom starts at S=0 at high coverages and increases to S=1/2 as the coverage is decreased, which agrees very well with results obtained from STM experiments. At higher values of U, the spin of Ti is found to be close to 1 regardless of coverage. We also calculate the exchange coupling for Ti dimers on the Cu2N/Cu(100) surface and we find that the exchange coupling across a 'void' of 3.6Å is antiferromagnetic, whereas indirect (superexchange) coupling through a N atom is ferromagnetic. For a square lattice of Ti on Cu2N/Cu(100), we nd a novel spin striped phase.