Singlet ground state and magnetic interactions in new spin dimer system Ba3Cr2O8

We have successfully synthesized Ba3Cr2O8 and investigated its crystal structure and magnetic properties. The crystal structure consists of Ba2+ cations and isolated CrO43- tetrahedra; magnetic chromium ions exist as rare Cr5+ (3d(1), S = 1/2). An S = 1/2 compound Ba3Cr2O8 was found to be a three-dimensional quantum spin system with a singlet ground state of dimer origin. From the analysis of magnetic susceptibility and high-field magnetization data, excitation gap is evaluated as Delta/k(B) = 16.1 K and intra- and interdimer exchange interactions are estimated as J(0)/k(B) = 25.0 K and J'/k(B) 7.7 K, respectively. Comparing with a similar spin dimer compound Ba3Mn2O8, Ba3Cr2O8 has a more dominant intradimer interaction.