Tilted Spins in\nChains of Molecular Switches on Pb(100)

A complex based on\na Ni(II) porphyrin exhibiting spin\ncrossover\non Ag(111) is studied on Pb(100) by scanning tunneling microscopy\nat 0.3 K. Strong molecular interactions between the phenyl and pentafluorophenyl\nmoieties lead to the formation of molecular chains and cause a faceting\nof the substrate surface. The chains are located along double and\nmultiple substrate steps that deviate from high-symmetry directions.\nTunneling spectroscopy reveals spin-flip excitations of an <i>S</i> = 1 system. Measurements in high magnetic fields are used\nto identify a tilt of the complex and its hard anisotropy axis with\nrespect to the surface normal. Electron injection into the substrate\nnear the molecular rows induces a transition to a state with larger\ninelastic cross section, leaving the spin state unchanged.