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 Ba 3 Cr 2 O 8 and Sr 3 Cr 2 O 8 . For Ba 3 Cr 2 O 8 , the real part dielectric constant e ′( T ) exhibit a frequency-independent peak near the Jahn-Teller transition temperature T JT = 70 K. However, no anomaly in the e ′( T ) curve is observed near T JT = 275 K for the isostructural compound Sr 3 Cr 2 O 8 . The difference in the e ′( 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 Cr 5+ ions and the χ ( T ) curves can be described by the Bleaney–Bowers equation for both compounds.