Magnetic Ordering of AuCr: An Ultrasonic Investigation
The magnetic properties of the noble metal-3d transition metal spin glass alloys show a number of unusual characteristics, as summarized in the experimental review paper by Mydosh.1 In particular, the sharp peaks in the magnetic susceptibility which scale systematically with transition metal concentration are suggestive of the onset of some kind of magnetic ordering. Recently a careful search has been made for evidence of such ordering in the specific heat, both for AuFe2 and CuMn3 spin glass alloys. No sharp changes were observed in the vicinity of the susceptibility peak temperature, To, although the previously reported4,5 linear dependence of the low temperature magnetic contribution to the specific heat, Cm, was confirmed, and in the case of CuMn,3 rounded maxima were observed at temperatures above To. Results of measurements of the changes in magnetic entropy in the same experiments2,3 indicate that fewer than one third of the transition metal ions participate in magnetic ordering between To and O K. Specific heat measurements of AuCr have also been carried out recently.6 Broad maxima were observed for a range of Cr concentration 0.02 at.% ⪝ C ⪝ 0.1 at.%, at temperatures which scale linearly with C. This region of concentration does not quite overlap that of the existing susceptibility data1,7 (0.2 at.% ⪝ C ⪝ 10 at.%).
KeywordsUltrasonic Velocity Aluminosilicate Glass Specific Heat Measurement Susceptibility Peak Ultrasonic Experiment
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- 6.T. Kemény, G.J. Nieuwenhuys and H. Algra, Low Temperature Physics — LT 14, Vol. V, ed. M. Krusius and M. Vuorio (to be published).Google Scholar