Inter-Molecule Interaction for Magnetic Property of Vanadyl Tetrakis(thiadiazole) Porphyrazine Film on Au(111)*

Metal phthalocyanine has been widely investigated and its magnetic behaviour of their film attracts much attention in relation to the spintronic application. Controlling the magnetic properties with changing molecule-assembly is a great challenge. However, it’s not easy to control the assembly with C-H terminated Pc molecules. Here, we investigate a film formation and a magnetic property of vanadyl-tetrakis(thiadiazole)porphyrazine(VOTTDPz) molecules on Au(111) with using STM.
Figure 1 shows the well-ordered film of VOTTDPz molecules on Au(111). Unlike the square-like lattice of VOPc on Au(111), the film shows the three-fold symmetry with nearest-neighbor distance of ~1.1 nm which is shorter than that of 1.4 nm for VOPc/Au(111), suggesting stronger attractive force than that formed by CH. Figure 2 shows a STS near the Fermi level. Sharp Kondo peaks derived from the molecules unpaired spin. The presence of a spin in VOTTDPz is consistent with previous EPR data and there exists S=1/2 at the V atom.
We detected asymmetric and weak Kondo peak for outer magnetic field of 0 T, which becomes strong and symmetric peak at 5 T, which is understood by the shift of the spin center of the Kondo resonance from V 3d to delocalized p state in ring with the magnetic field.