title: Spin Exchange Interaction in Substituted Copper Phthalocyanine Crystalline Thin Films.
abstract: The origins of spin exchange in crystalline thin films of Copper Octabutoxy Phthalocyanine (Cu-OBPc) are investigated using Magnetic Circular Dichroism (MCD) spectroscopy. These studies are made possible by a solution deposition technique which produces highly ordered films with macroscopic grain sizes suitable for optical studies. For temperatures lower than 2 K, the contribution of a specific state in the valence band manifold originating from the hybridized lone pair in nitrogen orbitals of the Phthalocyanine ring, bears the Brillouin-like signature of an exchange interaction with the localized d-shell Cu spins. A comprehensive MCD spectral analysis coupled with a molecular field model of a σπ - d exchange analogous to sp-d interactions in Diluted Magnetic Semiconductors (DMS) renders an enhanced Zeeman splitting and a modified g-factor of -4 for the electrons that mediate the interaction. These studies define an experimental tool for identifying electronic states involved in spin-dependent exchange interactions in organic materials.
authors.affiliation: University of Vermont, Department of Physics and the Materials Science Program, Burlington, 05405, USA.
authors.forename: Naveen
authors.initials: N
authors.lastname: Rawat
authors.affiliation: University of Vermont, Department of Physics and the Materials Science Program, Burlington, 05405, USA.
authors.forename: Zhenwen
authors.initials: Z
authors.lastname: Pan
authors.affiliation: University of Vermont, Department of Physics and the Materials Science Program, Burlington, 05405, USA.
authors.forename: Cody J
authors.initials: CJ
authors.lastname: Lamarche
authors.affiliation: University of Vermont, Department of Chemistry, Burlington, 05405, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Wetherby
authors.affiliation: University of Vermont, Department of Chemistry, Burlington, 05405, USA.
authors.forename: Rory
authors.initials: R
authors.lastname: Waterman
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, 32310, USA.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Tokumoto
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, 32310, USA.
authors.forename: Judy G
authors.initials: JG
authors.lastname: Cherian
authors.affiliation: University of Vermont, Department of Physics and the Materials Science Program, Burlington, 05405, USA.
authors.forename: Randall L
authors.initials: RL
authors.lastname: Headrick
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, 32310, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: McGill
authors.affiliation: University of Vermont, Department of Physics and the Materials Science Program, Burlington, 05405, USA.
authors.forename: Madalina I
authors.initials: MI
authors.lastname: Furis