In the first part of the talk I briefly review  recent experiments of inelastic scanning tunneling spectroscopy of single and a few magnetic atoms and molecules [1-6 ].   Then I show how these experiments can be  modeled with a phenomenological spin-assisted tunneling Hamiltonian so that the inelastic dI/dV line shape is related to the spin spectral weight of the magnetic atom [7]. This accounts for the   spin selection rules and dI/dV spectra observed experimentally for single Fe and Mn atoms deposited on Cu2N, as well as Iron Pthalocyanines and Mn chains.   In the final part of the talk I discuss how spin polarized STM can be used to manipulate the spin of the magnetic atoms and molecules [8].

1.A. J. Heinrich, J. A. Gupta, C. P. Lutz, and D. M. Eigler, Science 306, 466 (2004).
2.C. F. Hirjibehedin, C. P. Lutz, and A. J. Heinrich, Science 312, 1021 (2006).
3.C. Hirjibehedin et al., Science 317, 1199 (2007).
4.A. F. Otte et al., Nature Phys. 4, 847 (2008).
5.Xi. Chen et al., Phys. Rev. Lett. 101, 197208 (2008).
6.N. Tsukahara et al., Phys. Rev. Lett. 102, 167203 (2009).
7.J. Fernández-Rossier,  Phys. Rev. Lett. 102, 256802 (2009)
8.F. Delgado,  J. J. Palacios, J. Fernández-Rossier, in preparation