title: A star-shaped heteronuclear Cr(III)Mn(II)3 species and its precise electronic and magnetic structure: spin frustration studied by X-ray spectroscopic, magnetic, and theoretical methods.
abstract: Molecular magnets incorporate transition-metal ions with organic groups providing a bridge to mediate magnetic exchange interactions between the ions. Among them are star-shaped molecules in which antiferromagnetic couplings between the central and peripheral atoms are predominantly present. Those configurations lead to an appreciable spin moment in the nonfrustrated ground state. In spite of its topologically simple magnetic structure, the [Cr(III)Mn(II)(3) (PyA)(6)Cl(3)] (CrMn(3)) molecule, in which PyA represents the monoanion of syn-pyridine-2-aldoxime, exhibits nontrivial magnetic properties, which emerge from the combined action of single-ion anisotropy and frustration. In the present work, we elucidate the underlying electronic and magnetic properties of the heteronuclear, spin-frustrated CrMn(3) molecule by applying X-ray magnetic circular dichroism (XMCD), as well as magnetization measurements in high magnetic fields, density functional theory, and ligand-field multiplet calculations. Quantum-model calculations based on a Heisenberg Hamiltonian augmented with local anisotropic terms enable us not only to improve the accuracy of the exchange interactions but also to determine the dominant local anisotropies. A discussion of the various spin Hamiltonian parameters not only leads to a validation of our element selective transition metal L edge XMCD spin moments at a magnetic field of 5 T and a temperature of 5 K but also allows us to monitor an interesting effect of anisotropy and frustration of the manganese and chromium ions.
authors.affiliation: University of Osnabrück, Department of Physics, Barbarastrasse 7, D-49069 Osnabrück, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Prinz
authors.forename: Karsten
authors.initials: K
authors.lastname: Kuepper
authors.forename: Christian
authors.initials: C
authors.lastname: Taubitz
authors.forename: Michael
authors.initials: M
authors.lastname: Raekers
authors.forename: Sumit
authors.initials: S
authors.lastname: Khanra
authors.forename: Biplab
authors.initials: B
authors.lastname: Biswas
authors.forename: Thomas
authors.initials: T
authors.lastname: Weyhermüller
authors.forename: Marc
authors.initials: M
authors.lastname: Uhlarz
authors.forename: Joachim
authors.initials: J
authors.lastname: Wosnitza
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schnack
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Postnikov
authors.forename: Christian
authors.initials: C
authors.lastname: Schröder
authors.forename: Simon J
authors.initials: SJ
authors.lastname: George
authors.forename: Manfred
authors.initials: M
authors.lastname: Neumann
authors.forename: Phalguni
authors.initials: P
authors.lastname: Chaudhuri
mesh_terms: D016880:Anisotropy; D002857:Chromium / Q000737:chemistry*; D002942:Circular Dichroism; D004579:Electron Transport; D004583:Electrons; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D014965:X-Rays
chemical_list: D002857:Chromium; D008345:Manganese