Superconductivity of HoMo₆S₈ thin films

Films of HoMo₆S₈ approximately 0.5 microm thick have been prepared by co-deposition of the elements on a substrate held at an elevated temperature. As-prepared films do not exhibit superconductivity. Annealing in the presence of a flux of sulfur vapor for about one hour at 850°C lowers the resistivity, raises the resistivity ratio and brings about reentrant superconducting behavior similar to that observed in bulk polycrystalline samples. Subsequent annealing suppresses the reentry into the normal state even though the resultant film has a higher resistivity ration and appears to have a sharper upper resistive transition. These results are discussed in the context of both domain wall superconductivity and possible antiferromagnetism rather than ferromagnetism of the low temperature phase.