Magnetic-Field Induced Phase Transitions in a Weakly Coupled s=1/2 Quantum Spin Dimer System Ba3Cr2O8

By using bulk magnetization, electron spin resonance (ESR), heat capacity, and neutron scattering techniques, we characterize the thermodynamic and quantum phase diagrams of Ba3Cr2O8. Our ESR measurements indicate that the low field paramagnetic ground state is a mixed state of the singlet and the S-z=0 triplet for H perpendicular to c. This suggests the presence of an intradimer Dzyaloshinsky-Moriya (DM) interaction with a DM vector perpendicular to the c axis.