ANOMALOUS ELECTRICAL AND STRUCTURAL PROPERTIES OF DYSPROSIUM AND THULIUM THIN FILMS AT LOW TEMPERATURES

Ján Dudáš

   Thin films of dysprosium and thulium were prepared by evaporation in high vacuum (Dy.Tm) and in ultrahigh vacuum (UHV) in the thickness range from 16 nm to 370 nm. The size-effect of the electrical resistivity of these films is without anomalies and in qualitative agreement with theory. Investigation of the crystal structure of these films by means of X-ray diffraction showed that Dy films contained a phase with hcp structure of Dy and also a small amount of DyH₂, whereas Tm films (HV and UHV) consisted only of a single phase with hcp crystal structure of Tm. The resistivity vs. temperature dependences of Dy and Tm (UHV) measured in the low temperature region from 4.2 K up to the room temperature exhibit a knee-like (in thinner films) or hump-backed (thicker films) anomalies near the magnetic phase transition from the paramagnetic state to the antiferromagnetic state which are caused by the magnetic structure. Unusual $rho; vs. T anomalies were observed in two temperature regions in Tm films (HV) - below ∼60 K and near ∼170 K that could be caused by hydrogen present in the form of a solid solution in these films.

Keywords: electrical resistivity, thin films, dysprosium, thulium, low temperatures, crystal structure

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