尖晶石自旋玻璃CuGa_2O_4和CuAl_2O_4的零点熵
Zero-point entropy of the spinel spin glasses CuGa_2O_4 and CuAl_2O_4
摘要：
自旋玻璃的零点熵是一个很难用实验确定和解释的性质。自旋玻璃理论对零点熵的值提供了各种各样的预测，包括非物理的预测，但是实验结果一直缺乏。研究了CuGa_2 O_4和CuAl_2 O_4两种尖晶石型Cu ~（2+）基自旋玻璃的磁性和零点熵。直流和交流磁化率和比热测量表明这两种材料的许多特性自旋玻璃功能。自旋玻璃的凝固温度被确定为Tf = 2.89 +/- 0.05 K的CuGa 2 O 4和Tf = 2.30 +/- 0.05 K的CuAl 2 O 4。通过对比热数据的积分，我们发现CuGa_2 O_4和CuAl_2 O_4的零点熵分别为S_0 = 4.96JK ~（-1）mol ~（-1）和S_0 = 4.76JK ~（-1）mol ~（-1）。这些值最接近于Sherrington-Kirkpatrick XY自旋玻璃的预测，然而它们明显高于所有的理论预测。这表明CuGa 2 O 4和CuAl 2 O 4在其基态中具有比任何自旋玻璃模型更大的简并性。
英文摘要：
The zero-point entropy of a spin glass is a difficult property to experimentally determine and interpret. Spin glass theory provides various predictions, including unphysical ones, for the value of the zero-point entropy, however experimental results have been lacking. We have investigated the magnetic properties and zero-point entropy of two spinel Cu2+ based spin glasses, CuGa2O4 and CuAl2O4. Dc- and ac-susceptibility and specific heat measurements show many characteristic spin glass features for both materials. The spin glass freezing temperature is determined to be Tf = 2.89 +/- 0.05 K for CuGa2O4 and Tf = 2.30 +/- 0.05 K for CuAl2O4. By integrating the specific heat data we have found that CuGa2O4 and CuAl2O4 have zero-point entropies of S0 = 4.96 JK-1mol-1 and S0 = 4.76 JK-1mol-1 respectively. These values are closest to the prediction for a Sherrington-Kirkpatrick XY spin glass, however they are notably higher than all of the theoretical predictions. This indicates that CuGa2O4 and CuAl2O4 have a greater degeneracy in their ground states than any of the spin glass models.
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