Dielectric properties of the spin-1/2 dimer compounds Ba3Cr2O8 and Sr3Cr2O8

We have investigated the dielectric and magnetic properties of the spin-1/2 compounds Ba3Cr2O8 and Sr3Cr2O8. For Ba3Cr2O8, the real part dielectric constant epsilon'(T) exhibit a frequency-independent peak near the Jahn-Teller transition temperature T-JT = 70 K. However, no anomaly in the epsilon'(T) curve is observed near T-JT = 275 K for the isostructural compound Sr3Cr2O8. The difference in the epsilon'(T) behaviors may be attributed to the different onset temperatures of the phonon mode splitting in the samples. Dielectric relaxation analysis revealed that extrinsic contribution due to Maxwell-Wagner effect dominated at high temperatures for both compounds. The magnetization data reveal the occurrence of antiferro-magnetic interactions between the Cr5+ ions and the chi(T) curves can be described by the Bleaney-Bowers equation for both compounds. (C) 2014 Elsevier B.V. All rights reserved.