Effect of a ferromagnetic STM cobalt tip on a single Co-phthalocyanine molecule adsorbed on a ferromagnetic substrate

The effect of a ferromagnetic scanning tunneling microscope (STM) cobalt tip on the electronic, magnetic and electronic transport properties of a Co-phthalocyanine (CoPc)/Co(111) junction has been investigated in the framework of density functional theory in conjunction with Landauer transport and the non-equilibrium Green function formalism. It is shown that the spin magnetic moment of the CoPc molecule can be flipped by varying the distance between the STM tip and the CoPc molecule when passing from the tunneling regime to the contact regime. Our calculations show that such spin flip of the CoPc molecule leads to a change of the sign of the Tunneling Magneto-Resistance ratio (TMR). The change from the tunneling to contact regime also leads to large changes in the total and spin-polarized I–V characteristics.