Lowering of magnetic field intensity at the surfaces of alpha-Fe2O3 and FeBO3 single crystals

Depth-selective conversion electron Mossbauer spectroscopy was used to stud y magnetic properties of the thin surface layers of the alpha-Fe2O3 and FeB O3 single crystals. An analysis of the experimental spectra indicates that the magnetic properties of the layers at a depth of more than similar to 10 0 nm from the surface are similar to the properties of crystal bulk, and th e corresponding spectra consist of narrow lines. The lines gradually broade n as the crystal surface is approached. The spectra of the similar to 10-nm -thick surface layers consist of broad lines, indicating a wide distributio n delta = 2.1 T of the effective magnetic field about its mean value of 32. 2(4) T. The experimental spectra were used to determine the effective magne tic fields (H-eff) for the iron ions situated in the surface layers of thic kness similar to 100 nm. The effective fields in these layers were found to gradually decrease at room temperature (291 K) as the crystal surface was approached. The H-eff values in the 2.4(9)-nm-thick surface layer of the al pha-Fe2O3 crystal and 4.9(9)-nm layer of FeBO3 are 0.7(2) and 1.2(3)%, resp ectively, smaller than for the nuclei of the ions in the bulk of these crys tals. (C) 2000 MAIK "Nauka/Interperiodica".