Molecular Magnet:

One of our interests is to investigate various physical realizations of single spin and choose the most suitable for future inspection of spin dynamics. At the smallest scale of single spin there is the unique magnetic atom. For the purpose of applications it is necessary to efficiently control the magnetization of our single spin. A highly promising route is to dress the spin of magnetic atoms (3d or 4f) with an organic shell to create the so-called molecular magnet. These are the most appealing because recent studies have opened up the possibility of controlling both the spin properties (magnetic moment and anisotropy) as well as the spatial ordering of the magnetic spins via molecular self assembly 1,2. The number of available molecular magnets is considerable; therefore, I have limited my presentation to only two systems which seem the most suitable for my purposes. Both systems are extremely attractive because they are incredibly versatile and they are planar allowing easy access to the spins with the STM tip. Porphyrin-based molecular magnets 3 can host both 3d transition metals and 4f rare earth magnetic atoms. They can be dressed with different radicals which play a crucial role in the coupling of the magnetic center with the substrate. Stable magnetization has been experimentally demonstrated with X-ray Magnetic Circular Dichroism (XMCD)4. The second class of molecular magnets is created through metallosupramolecular chemistry where 3d transition metal atoms bridge organic tectons to forms ordered lattices 1,2. A recent combined STM-XMCD study of this class of molecular magnet emphasizes their versatility: the anisotropy of Fe atoms linked by 1,4-benzenedicarboxylic acid on Cu 111 can be tuned through oxidation 1. STM exploration of molecular magnet adsorbed on surfaces is only in its infancy, even more when combined with spin polarized measurement. To my knowledge there is only one publication presenting a SP-STM of molecular magnets, in this case cobalt phthalocyanine 5.

[1]Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface.
P. Gambardella, S. Stepanow, A. Dmitriev, J. Honolka, F. DeGroot, M. Lingenfelder, S. Sen Gupta, D. Sarma, P. Bencok, S. Stanescu, S. cahir, S. Pons, N. Lin, A. Seitsonen, H. Brune, J. Barth, K. Kern..
Nature Materials 8 2009 189

[2]Molecular Architectonic on Metal Surfaces
J.V. Barth
Annu. Rev. Phys. Chem. 2007 58:375-407

[3]Visualizing the Frontier Orbitals of a Conformationally Adapted Metalloporphyrin
A. Weber-Bargioni, W. Auwarter, F. Klappenberger, J. Reichert, S. Lefrancois, T. Strunskus, C. Wçll, A. Schiffrin, Y. Pennec and J. V. Barth.
ChemPhysChem 2008, 9, 89-94

[4]Substrate-induced magnetic ordering and switching of iron porphyrin molecules
H. Wende, M. Bernien, J. Luo, C. Sorg, N. Ponpandian, J. Kurde, J. Miguel, M. Piantek, X. Xu, P. Eckhold, W. Kuch, K. Baberschke, P. Panchmatia, B. Sanyal, P. Oppeneer and O. Eriksson.
Nature Materials 6 2007 516

[5]Visualizing the Spin of Individual Cobalt-Phthalocyanine Molecules
C. Iacovita,M. V. Rastei, B. W. Heinrich, T. Brumme, J. Kortus, L. Limot, and J. P. Bucher
Phys. Rev. Lett. 101, 116602 (2008)