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MA: Fachverband Magnetismus

MA 28: Surface Magnetism I (jointly with O)

MA 28.2: Talk

Wednesday, March 9, 2016, 09:45–10:00, H31

Co-Salen on NiO(001): Indication of a superexchange mediated coupling between a magnetic molecule and an antiferromagnetic bulk insulating substrate — •Alexander Schwarz, Josef Grenz, and Roland Wiesendanger — INF (IAP), Fachbereich Physik, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg

Spin Polarized Scanning Tunneling Microscopy (SP-STM) and X-ray magnetic circular dichroism (XMCD) have been employed to detect the magnetic coupling between a magnetic surface and magnetic molecules adsorbed on top [1,2]. However, up to now only metallic substrates were investigated.

Here, we utilize Magnetic Exchange Force Microscopy (MExFM), which can be applied to insulating sample system [3]. This enables us to study the magnetic coupling between Co-Salen and the row-wise antiferromagnetically ordered spins on the (001) surface of a NiO single crystal, a wide band gap insulator. Using magnetically coated tips we find that Co-Salen molecules, which adsorb on neighboring oxygen rows, exhibit a significantly different apparent height. This observation can be explained by a magnetic contribution to the total tip-sample interaction. As on this substrate the molecule adsorbs with its central cobalt atom above oxygen, a superexchange mechanism could be responsible for the magnetic coupling between the spin-carrying nickel atoms of the subsurface layer and the cobalt atoms of the molecules.

[1] H. Wende at al., Nature Mat. 6, 516 (2007).

[2] C. Iacovita et al., Phys. Rev. Lett. 101, 116602 (2008).

[3] U. Kaiser, A. Schwarz, R. Wiesendanger, Nature 446, 522 (2007).