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.