Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 65: Surface and Interface Magnetism II (jointly with MA)
O 65.9: Talk
Thursday, March 14, 2013, 12:30–12:45, H33
Modifying the magnetic properties of adsorbed spin bearing porphyrins by chemical stimuli — •Jan Girovsky1, Christian Wäckerlin1, Kartick Tarafder2, Jan Nowakowski1, Dorota Siewert1, Tatjana Hählen1, Aneliia Shchyrba3, Armin Kleibert1, Frithjof Nolting1, Thomas A. Jung1, Peter M. Oppeneer2, and Nirmalya Ballav4 — 1Paul Scherrer Institut, Switzerland — 2Uppsala University, Sweden — 3Universtity of Basel, Switzerland — 4Indian Institute of Science Education and Research (IISER-Pune), India
Metalloporphyrins adsorbed on and exchange coupled to ferromagnetic substrates [1], have been stimulated by different axial ligands like NO and NH3. Beyond the modification of the electronic states in the ad-molecule by the chemical ligation [2], we now focus on the sign and strength of the exchange interaction with the substrate [3,4]. In our experimental (XMCD, STM, XPS) and theoretical (DFT+U) work we provide evidence for cooperativity between the axial ligand on top and the surface ligand below the porphyrin ("surface spin trans effect"). We present four magneto-chemical effects: reduction (HS → IS), quenching (S ≠ 0 → S=0), flipping ("S > 0" → "S < 0" ) and induction (S = 0 → S ≠ 0) of magnetic moments in specific ad-porphyrins upon coordination with different chemical ligands.
[1] A. Scheybal et al, Chem Phys Lett 411, 214 (2005).
[2] W. Hieringer et al, J Am Chem Soc 133, 6206 (2011).
[3] C. Wäckerlin et al, Nat Comms 1, 61 (2010).
[4] C. Wäckerlin et al, Chem. Science 3, 3154 (2012).