Depth Selective Mossbauer Analysis on a Barium Hexaferrite Single Crystal with a New UHV Orange Spectrometer

Abstract
To study the hyperfine interaction as function of depth in a solid sample a new ultrahigh vacuum magnetic spectrometer has been designed and built for depth selective Mossbauer spectroscopy. To cope with the low intensity of emitted electrons in such an experiment the magnetic spectrometer of the orange type combines a high transmission of ≈ 20 % of 4π with an adjustable energy resolution in the order of 0.2 to 2 %. Furthermore, the focusing has been optmised to allow the simultaneous registration of events in an energy band of ±4% of the selected energy. The multi channel detector will provide 8 azimuthal and 5 energy channels. First ⁵⁷Fe-Mossbauer experiments on magnetic single crystals have been performed to look for a variation of the magnetic hyperfine field with depth in the sample. The feasibility of this non-destructive depth selective analysis in studying surface magnetism of bulk samples has been demonstrated on a non-enriched BaFe₁₂O₁₉ single crystal.