Spin exchange interaction in quasi-1D Cu-phthalocyanine crystalline thin film measured by Magnetic Circular Dichroism (MCD) spectroscopy

ORAL

Abstract

Highly-oriented Cu-phthalocyanine (PC) pen-written crystalline thin films can be viewed as quasi-1D spin 1/2 magnetic chains. In order to reveal the nature of spin exchange between localized S=1/2 Cu spins, MCD spectroscopy was performed on films with millimeter-sized grains fabricated from a soluble CuPc derivative in magnetic fields up to 10 Tesla at temperatures ranging from 0.4 K to 77K. At T$<$2K and B$<$4T the MCD associated with transitions between Q-band $\pi$ electron states exhibits a non-linear temperature-dependent Brillouin-like increase with magnetic field. For B$>$4T the MCD evolves linearly with magnetic field, as expected from diamagnetic carbon-based systems. Theoretical modeling\footnote{W. Wu et. al.,PRB 84,024427(2011)} of electronic structure and exchange interactions in this system predicts an indirect exchange mechanism mediated by delocalized ligand states. Our MCD measurements identified the states responsible for this exchange.

–

Authors

  • Zhenwen Pan

    • Material Science and Physics Dept.,University of Vermont

  • Naveen Rawat

    • Material Science and Physics Dept.,University of Vermont

  • Cody Lamarche

    • Material Science and Physics Dept.,University of Vermont

  • Takahisa Tokumoto

    • National High Magnetic Field Laboratory

  • Anthony Wetherby

    • Chemistry Dept., University of Vermont

  • Rory Waterman

    • Chemistry Dept., University of Vermont

  • Randy Headrick

    • Material Science and Physics Dept.,University of Vermont

  • Steve Mcgill

    • National High Magnetic Field Laboratory

  • Madalina Furis

    • Material Science and Physics Dept.,University of Vermont