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

•Dielectric and magnetic properties of Ba3Cr2O8 and Sr3Cr2O8 were investigated.•A peak of ε′(T) near TJT was observed only in Ba3Cr2O8 but not for Sr3Cr2O8.•The ε′(T) behaviors may be due to the difference of the phonon mode splitting.

We have investigated the dielectric and magnetic properties of the spin-1/2 compounds Ba3Cr2O8 and Sr3Cr2O8. For Ba3Cr2O8, the real part dielectric constant ε′(T) exhibit a frequency-independent peak near the Jahn-Teller transition temperature TJT = 70 K. However, no anomaly in the ε′(T) curve is observed near TJT = 275 K for the isostructural compound Sr3Cr2O8. The difference in the ε′(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 antiferromagnetic interactions between the Cr5+ ions and the χ(T) curves can be described by the Bleaney–Bowers equation for both compounds.