Local zero-bias anomaly in tunneling spectra of a transition-metal oxide thin film

Abstract

The electronic structure around the Fermi energy of a thin film of iron monoxide on Pt͑111͒ is studied using low temperature scanning tunneling spectroscopy. The surface exhibits a coincidence structure ͑Moiré pattern͒ due to a lattice mismatch between the oxide thin film and the metal substrate. While the local density of states around the Fermi energy is featureless at most positions in the unit cell, a pronounced depression is observed at one particular site. The origin of this local zero-bias anomaly is discussed in relation to results from first-principle calculations. As a preliminary conclusion, it is suggested that the anomaly is a Kondo resonance due to a frustrated antiferromagnetic layer.

Interplay between structural, magnetic, and electronic properties in aFeO∕Pt(111)ultrathin film

“…The AFM and AFI orderings are very similar in energy and clearly more stable than the FM one. Our results on the pseudomorphic models, although consistent with the results of ferromagnetic resonance spectroscopy measurements, which show that the film is not ferromagnetically ordered, 56 do not exclude a possible existence of a more complex magnetic ordering, driven by the local structure of the interface. The calculated overall structural characteristics agree very well with the experimental estimates.…”

“…The weak sitedependent magnetization on Pt could have a role in the zero-bias conductance anomaly observed by STS in the Fe-top region of the Moiré pattern, which is tentatively assigned to the Kondo effect. 56 Turning now to the estimation of the change in work function Δφ induced by the oxide layer, we note that Δφ depends strongly on the structure of the interface and on its magnetic order, and that its modulation is mainly due to the peculiarity of the Fe-top structure. For instance, for the most stable CO-AFI-(√3×√3)R30° structure, Δφ is 0.30-0.40 eV for most configurations, except the Fe-top site, where Δφ is −0.37 eV, Table 2.…”

Zero-bias conductance anomaly of a FeO-bound Au atom triggered by CO adsorption

“…For the pristine film, such dip in the dI / dV signal was recently observed in a localized region of the coincidence lattice that forms between the FeO layer and the Pt support. 11 A similar response is now revealed for other oxide regions too, however, only after the adsorption of goldcarbonyl species. Apparently, the binding of AuCO modifies the FeO magnetic structure in a way that it becomes susceptible to spin-flip scattering processes with the Pt conduction electrons.…”

“…And second, a comparable conductance behavior is observed even without AuCO on the FeO top domains. 11 At this particular position of the Moiré cell, a similar antiresonance appears in the dI / dV spectra that is only slightly sharper ͑FWHM of 86 meV͒ and less pronounced than in the AuCO case ͓Fig. 3͑a͔͒.…”

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

“…This finding is in agreement with paramagnetic resonance spectroscopy, which did not reveal a ferromagnetic spin signal from the FeO film. 301 In both, the pseudomorphic and the non-pseudomorphic computational cells, the oxide regions with Fe in hcp and fcc binding sites have rather similar properties independent of the assumed magnetic structure, whereas the top domain sticks out in various aspects. It is characterized by the largest interfacial separation from the Pt (111) Assuming that the pronounced contrast in STM images taken at elevated sample bias is indeed governed by modulations of the surface potential ( Fig.…”