Determination of site specific interatomic forces between an iron coated tip and the NiO(001) surface by force field spectroscopy

Three-dimensional force fields have been measured in ultrahigh vacuum at low temperatures on a well defined NiO(001) surface by atomic force microscopy in the dynamic mode of operation. With an atomically sharp iron coated tip, atomic resolution is obtained close to the surface, whereby individual force curves can unequivocally be assigned to specific lattice sites. The total force at each lattice site can be separated into long- and short-range contributions. Long-range forces are fitted to a 1/z power law. Short-range interactions show good agreement with a Morse potential and have significantly different interaction energies and characteristic interaction lengths at the oxygen and nickel sites, respectively. No systematic deviations at neighboring lattice sites were found, which could be attributed to the detection of exchange interactions between the spins of the iron coated tip and nickel sites. (C) 2003 Elsevier Science B.V. All rights reserved.