Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65

MA 20.159: Poster

Montag, 7. März 2005, 14:00–18:00, Poster TU C

Electronic and magnetic properties of Fe (II) based molecular magnets — •F. Gouider¹, J. Kreitlow¹, D. Baabe¹, S. Süllow¹, J. Litterst¹, R. Feyerherm², A. Loose², T. Ishida³, T. Nogami³, K. Doll⁴, and H.-H. Klauss¹ — ¹Institut für Metallphysik und Nukleare Festkörperphysik, TU Braunschweig — ²Hahn-Meitner-Institut, 14109 Berlin — ³Dep. of Appl. Phys. and Chem., University Chofu, Tokyo 182-8585, Japan — ⁴Institut für Mathematische Physik, TU Braunschweig

We present Moessbauer spectroscopy studies on two Fe(II) S=2 based molecular magnets, FePM₂Cl₂ and FePMCl₂ (PM=N₂C₄H₄ = pyrimidine). In both compounds the pyrimidine molecule forms the magnetic exchange path. FePM₂Cl₂ crystallizes in a chiral lattice. Combined magnetization, Moessbauer spectroscopy, and powder neutron diffraction studies reveal that it is a canted antiferromagnet below T_N=6.4 K with an unusually large canting of the magnetic moments of 14^∘ from their general antiferromagnetic alignment. This results in weak ferromagnetism with a ferromagnetic component of ≈1 µ_B[1]. In FePMCl₂ anisotropic magnetic interactions are provided via the PM molecules and the Cl⁻ ions. This leads to a long range magnetic order below ≈ 11 K. Although neutron scattering results in an ordered moment of 3.2 µ_B the Moessbauer experiments reveal a strongly reduced magnetic hyperfine field of ≈ 4 T. These results are discussed in terms of the interplay of orbital and spin magnetic moments on the local Fe complexes. [1] R. Feyerherm et al., PRB 69 (2004) 134427.