Polaronic behavior of Mn₄O₄heterocubane clusters in LiMn₂O₄spinel

Abstract

Microsymposiaheat measurements.Spin glasses provide an important class of frustrated magnets.Typically based on disordered systems, they have found relevance in diverse areas of research, such as neural networks, the origin of life, and algorithm theory.Despite the theoretically prediction that these materials have a non-zero residual entropy, there have been no clear experimental studies of the entropy of a spin glass.This presentation describes an experimental study of the magnetic properties and zero point entropy of a series of S=1/2 spin glasses.Diamagnetic dilution in the spinel systems CuAl2O4 and CuGa2O4 forms isomorphic solid solutions ZnxCu(1-x)Ga2O4 and ZnxCu(1-x) Al2O4 that provides an opportunity to investigate the effect that nonmagnetic substitution has on the spin glass properties of CuGa2O4 and on the entropy of the related spin glass states.Low temperature specific heat measurements were carried out on both CuGa2O4 and CuAl2O4 in order to determine the magnetic entropies, and compare them with the value theoretically predicted for S = 1/2 spin glasses.Both spinels were found to possess a non-zero magnetic entropy at 0K, with values that are significantly greater than the predicted value.These studies also indicate that the ground state degeneracy of these frustrated magnets can be controlled by chemical substitution.