Low energy ion scattering from the single crystal magnetite and from magnetite covered by condensed xenon at the Verwey transition

Energy spectra of He+, Ne+, Ar+ and Kr+ ions, scattered from a cleavage surface of a single crystal of magnetite, have been measured in small-angle geometry and in the temperature range of 85-300 K. The large energy losses of scattered ions and a very deep minimum around 120 K in the temperature dependence curve of ion yield (R+(T)) have been observed for all bombarding ions. The large energy losses were well explained in the frame of the zigzag collisions of incoming ions with Fe ions forming the surface semi-channels. The minimum in the R+(T) curve corresponding to the Verwey phase transition of magnetite can be explained by a change of the neutralization probability of incoming and outgoing ions, by a change of the target material transparency and by a change in the number of the trajectories containing ionizing collisions. The trajectory effect is visible especially for Ne+ and Ar+ ion interactions. Large suppression of the phase transition effect on ion scattering was observed on the magnetite surface covered by layers of condensed xenon. (C) 1999 Elsevier Science B.V. All rights reserved.