Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)
MA 40.2: Poster
Friday, March 27, 2009, 11:00–14:00, P1A
Magnetic properties of novel binuclear metal-organic complexes — •A. Parameswaran1, Y. Krupskaya1, R. Klingeler1, V. Kataev1, I. Bezkishko2, V. Miluykov2, O. Kataeva2, O. Sinyashin2, and B. Büchner1 — 1IFW Dresden, D-01171 Dresden, Germany — 2Arbuzov Institute for Organic and Physical Chemistry, RAS, Kazan, Russia
We present static magnetization and ESR data on novel binuclear complexes containing two transition metal ions TM = Mn or Ni connected by two 1,2-diphosphocyclopentadienide bridges for different ligands L = CO, MeCN and PPh3. In the case of TM = Mn, the effective moment peff is in average close to that of the Mn(II) in the low spin state. However, we find a systematic substantial increase of peff by passing from L = CO (peff = 1.55µB) via L = MeCN (2.2µB) to L = PPh3 (peff = 2.67 µB). The antiferromagnetic (AFM) Curie-Weiss temperatures amount to 1 K, 17 K and 18 K for these ligands, respectively. A systematic change of ESR spectra confirms these observations and reveals an appreciable anisotropy of the Mn - Mn AFM exchange due to the spin-orbit coupling effects. We conclude that by changing the ligand from a strong π-acceptor type (CO) to a weak one (PPh3) one can tune the electron density at the TM ion thereby affecting its local moment, the strength and the anisotropy of the intramolecurar magnetic exchange. Similarly strong effects are also visible in the Ni analogs. Surprisingly, however, for Ni complexes the magnetic interaction changes to ferromagnetic and is larger in magnitude compared to the Mn counterpart.