AVS 51st International Symposium
    Nanometer-scale Science and Technology Monday Sessions
       Session NS-MoA

Paper NS-MoA10
Magnetic Interaction between a Ferromagnetic Substrate and Adsorbed Manganese Porphyrin Molecules

Monday, November 15, 2004, 5:00 pm, Room 213D

Session: Magnetic Imaging and Spectroscopy
Presenter: T. Ramsvik, Paul Scherrer Institute, Switzerland
Authors: A. Scheybal, Paul Scherrer Institute, Switzerland
T. Ramsvik, Paul Scherrer Institute, Switzerland
R. Bertschinger, Paul Scherrer Institut, Switzerland
M. Putero-Vuaroqueaux, L2MP-CNRS, France
T.A. Jung, Paul Scherrer Institute, Switzerland
Correspondent: Click to Email
The magnetic interaction between a magnetized thin film cobalt substrate and adsorbed manganese(III)-tetraphenylporphyrin chloride (MnTPPCl) molecules has been studied using X-ray magnetic circular dichroism (XMCD). In the regime of submonolayer coverage a clear circular dichroism is observed at the Mn L@sub 32@-edge, verifying that a net magnetization is set up by the manganese ions in the adsorbed molecules. An element specific hysteresis study shows that the magnetic properties of the molecules mirror those of the cobalt substrate. From this and from temperature dependent studies it is concluded that exchange interaction between the cobalt film and the molecules is the dominant cause for this induced magnetism. To our knowledge, this is the first time that an exchange coupling between adsorbed organic molecules and a ferromagnetic substrate has been demonstrated by XMCD at 3d-transition metal L@sub 32@-edges, thereby allowing direct information about both orbital and spin magnetic moments@footnote 1@. As MnTPPCl is the parent compound of the [Mn(III)-porphyrin][TCNE] family of molecular magnets (TCNE = tetracyanoethylene)@footnote 2@, the here presented molecular system and experiment provides a model system for the study of the magnetic interaction at the interface between a conventional ferromagnet and a molecular magnet. Furthermore, an organic semiconductor like tris(8-hydroxyquinoline) aluminium (Alq@sub 3@) can be used to prepare an organic spin-valve exhibiting giant magnetoresistance, as it has been demonstrated recently.@footnote 3@ Thus, the understanding of local magnetic coupling in molecular materials is of utmost importance for the application of magnetic materials in ever smaller dimensions. @FootnoteText@ @footnote 1@ G. Schütz et al., Phys. Rev. Lett. 58 (1987) 737@footnote 2@ J.S. Miller et al., Adv. Mat. 4 (1992) 498@footnote 3@ Z.H. Xiong et al., Nature 427 (2004) 821.