title: Spin tuning of electron-doped metal-phthalocyanine layers.
abstract: The spin state of organic-based magnets at interfaces is to a great extent determined by the organic environment and the nature of the spin-carrying metal center, which is further subject to modifications by the adsorbate-substrate coupling. Direct chemical doping offers an additional route for tailoring the electronic and magnetic characteristics of molecular magnets. Here we present a systematic investigation of the effects of alkali metal doping on the charge state and crystal field of 3d metal ions in Cu, Ni, Fe, and Mn phthalocyanine (Pc) monolayers adsorbed on Ag. Combined X-ray absorption spectroscopy and ligand field multiplet calculations show that Cu(II), Ni(II), and Fe(II) ions reduce to Cu(I), Ni(I), and Fe(I) upon alkali metal adsorption, whereas Mn maintains its formal oxidation state. The strength of the crystal field at the Ni, Fe, and Mn sites is strongly reduced upon doping. The combined effect of these changes is that the magnetic moment of high- and low-spin ions such as Cu and Ni can be entirely turned off or on, respectively, whereas the magnetic configuration of MnPc can be changed from intermediate (3/2) to high (5/2) spin. In the case of FePc a 10-fold increase of the orbital magnetic moment accompanies charge transfer and a transition to a high-spin state.
authors.affiliation: Department of Materials, ETH Zürich , Hönggerbergring 64, 8093 Zürich, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Stepanow
authors.forename: Alberto
authors.initials: A
authors.lastname: Lodi Rizzini
authors.forename: Cornelius
authors.initials: C
authors.lastname: Krull
authors.forename: Jerald
authors.initials: J
authors.lastname: Kavich
authors.forename: Julio C
authors.initials: JC
authors.lastname: Cezar
authors.forename: Flora
authors.initials: F
authors.lastname: Yakhou-Harris
authors.forename: Polina M
authors.initials: PM
authors.lastname: Sheverdyaeva
authors.forename: Paolo
authors.initials: P
authors.lastname: Moras
authors.forename: Carlo
authors.initials: C
authors.lastname: Carbone
authors.forename: Gustavo
authors.initials: G
authors.lastname: Ceballos
authors.forename: Aitor
authors.initials: A
authors.lastname: Mugarza
authors.forename: Pietro
authors.initials: P
authors.lastname: Gambardella
mesh_terms: D002942:Circular Dichroism; D004583:Electrons; D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D008672:Metals, Alkali / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling; D009942:Organometallic Compounds / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D007211:Indoles; D054833:Isoindoles; D008672:Metals, Alkali; D019216:Metals, Heavy; D009942:Organometallic Compounds; C013647:phthalocyanine