The zero-point entropy of a spin glass is a dificult 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 0:05K for CuGa2O 4 and Tf = 2:30 0:05K for CuAl2O4. By integrating the specific heat data we have found that CuGa2O 4 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 CuAl2O 4 have a greater degeneracy in their ground states than any of the spin glass models.
ASJC Scopus subject areas
- Physics and Astronomy(all)