Surface Investigations of Selected Materials by Low-Energy Ion Scattering Technique

Surfaces of three selected materials were investigated by means of low-energy ion-scattering technique: (1) the magnetite (Fe$\text{}_{3}$O$\text{}_{4}$) exhibiting the so-called Verwey transition (T$\text{}_{V}$(bulk)=125 K) accompanied by a small cubic-monoclinic crystal distortion, (2) the intermetallic compound NdMn$\text{}_{2}$ undergoing an antiferromagnetic-paramagnetic phase transition (T$\text{}_{N}$=104 K) accompanied by a large crystal distortion with a volume change of 1%, and (3) the typical insulator BaTiO$\text{}_{3}$ with two structural transitions below 300 K. The primary energy of the (Ne$\text{}^{+}$, Ar$\text{}^{+}$) ion beam was in the range of 4-8 keV, and the low-energy ion-scattering spectra were collected in the temperature range of 85-300 K. A large influence from the Verwey transition on the neutralization and re-ionization of scattered ions from magnetite surface was observed, while no visible change at the magnetic phase transition in NdMn$\text{}_{2}$ was revealed in the low-energy ion-scattering spectra. A strong dependence of the characteristics of the low-energy ion-scattering spectra on the irradiated time was observed for BaTiO$\text{}_{3}$ indicating that this surface was heavily charged by ion bombardments.