  Experimental observations of a peculiar behavior observed on heating and
cooling ${\rm Sb_2Te_3}$ films at different heating and cooling rate are
detailed. The film regained its original resistance, forming a closed loop, on
the completion of the heating-cooling cycle which was reproducible for
identical conditions of heating and cooling. The area enclosed by the loop was
found to depend on (i) the thickness of the film, (ii) the heating rate, (iii)
the maximum temperature to which film was heated and (iv) the cooling rate. The
observations are explained on basis of model which considers the film to be a
resultant of parallel resistances. The film's finite thermal conductivity gives
rise to a temperature gradient along the thickness of the film, due to this and
the temperature coefficient of resistance, the parallel combination of
resistance changes with temperature. Difference in heating and cooling rates
give different temperature gradient, which explains the observed hysteresis.
