title: Studies of a Large Odd-Numbered Odd-Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8 Mn.
abstract: The spin dynamics of Cr8 Mn, a nine-membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8 Mn is a rare example of a large odd-membered AF ring, and has an odd-number of 3d-electrons present. Odd-membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated-spin ground states. The chemical synthesis and structures of two Cr8 Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground-spin-state crossing from S=1/2 to S=3/2 in Cr8 Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin-pair correlations and scalar-spin chirality, shows a non-collinear spin structure that fluctuates between non-planar states of opposite chiralities.
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. bakerml@stanford.edu.|Institut Laue-Langevin, BP 156, 6 rue Jules Horowitz, 38042, Grenoble Cedex 9, France. bakerml@stanford.edu.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Baker
authors.affiliation: Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Lancaster
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, 43124, Parma, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Chiesa
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, 43124, Parma, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Amoretti
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Baker
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Claire
authors.initials: C
authors.lastname: Barker
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU, UK. Stephen.Blundell@physics.ox.ac.uk.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blundell
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, 43124, Parma, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Carretta
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: David
authors.initials: D
authors.lastname: Collison
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, 3000, Bern, Switzerland.
authors.forename: Hans U
authors.initials: HU
authors.lastname: Güdel
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Guidi
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Eric J L
authors.initials: EJ
authors.lastname: McInnes
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU, UK.
authors.forename: Johannes S
authors.initials: JS
authors.lastname: Möller
authors.affiliation: Institut Laue-Langevin, BP 156, 6 rue Jules Horowitz, 38042, Grenoble Cedex 9, France.
authors.forename: Hannu
authors.initials: H
authors.lastname: Mutka
authors.affiliation: Institut Laue-Langevin, BP 156, 6 rue Jules Horowitz, 38042, Grenoble Cedex 9, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Ollivier
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK.
authors.forename: Francis L
authors.initials: FL
authors.lastname: Pratt
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, 43124, Parma, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Santini
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Floriana
authors.initials: F
authors.lastname: Tuna
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, 3000, Bern, Switzerland.
authors.forename: Philip L W
authors.initials: PL
authors.lastname: Tregenna-Piggott
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Iñigo J
authors.initials: IJ
authors.lastname: Vitorica-Yrezabal
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Grigore A
authors.initials: GA
authors.lastname: Timco
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. Richard.Winpenny@manchester.ac.uk.
authors.forename: Richard E P
authors.initials: RE
authors.lastname: Winpenny
keywords: inelastic neutron scattering; molecular magnetism; muon spin relaxation; spin chirality; spin frustration