Electron paramagnetic resonance evidence for Jahn-Teller glasses

Abstract

Single crystal E.P.R. studies of copper as a dopant in lithium potassium sulphate, lithium ammonium sulphate and lithium sodium sulphate have been carried out from room temperature down to 77K. The three Jahn-Teller (JT) systems behave very similarly to one another. The room temperature dynamic JT spectra with g_iso = 2.19 ± 0.01 and A_iso = ±(33 ± 4)× 10^-4 cm^-1 transform around 247 K to spectra characterized by randomly frozen-in axial strains with g = 2.4307 ± 0.0005, g = 2.083 ± 0.001, A = ±(116 ± 2) × 10^-4 cm^-1 and A = ±(14 ± 4) ×10^-4 cm^-1. We proposed that the low temperature phase (below 247 K) of each of these systems provides an example of a Jahn-Teller glass.