Zero-point entropy of the spinel spin glasses CuGa 2O 4 and CuAl 2O 4 - Condensed Matter > Disordered Systems and Neural NetworksReport as inadecuate




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Abstract: The zero-point entropy of a spin glass is a difficult property toexperimentally determine and interpret. Spin glass theory provides variouspredictions, including unphysical ones, for the value of the zero-pointentropy, however experimental results have been lacking. We have investigatedthe magnetic properties and zero-point entropy of two spinel Cu2+ based spinglasses, CuGa2O4 and CuAl2O4. Dc- and ac-susceptibility and specific heatmeasurements show many characteristic spin glass features for both materials.The spin glass freezing temperature is determined to be Tf = 2.89 +- 0.05 Kfor CuGa2O4 and Tf = 2.30 +- 0.05 K for CuAl2O4. By integrating the specificheat data we have found that CuGa2O4 and CuAl2O4 have zero-point entropies ofS0 = 4.96 JK-1mol-1 and S0 = 4.76 JK-1mol-1 respectively. These values areclosest to the prediction for a Sherrington-Kirkpatrick XY spin glass, howeverthey are notably higher than all of the theoretical predictions. This indicatesthat CuGa2O4 and CuAl2O4 have a greater degeneracy in their ground states thanany of the spin glass models.



Author: L A Fenner, A S Wills, S T Bramwell, M Dahlberg, P Schiffer

Source: https://arxiv.org/



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