Systematic deviations were found below 0.003°K in the temperature dependence of nuclear orientation of Ce137m in cerous magnesium nitrate, using the temperature scale proposed by Daniels and Robinson. The temperature scale below 0.006°K was redetermined using a new method: nuclear orientation. This has the advantage over the 'Y-ray heating method of high sensitivity at the lowest temperature. The most striking result is hat a value of 1/T of 520, rather than the previously accepted 324, is obtained by demagnetization from initial condItions of 18.8 kG deg-1. The useful absolute temperature range is thus extended by at least 60% in 1/T. Auxiliary experiments on oriented Pm144 gave similar results and provided independent confirmation both of the inadequacy of the old temperature scale and of the validity of the new one.



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