Gazizulina, A.; Quintero-Castro, D.L.; Schilling, A.: Single-crystal growth and study of the mixed spin-dimer system Ba3-xSrxCr2O8. Physical Review B 96 (2017), p. 184201/1-7
10.1103/PhysRevB.96.184201

Abstract:
The compounds Sr3Cr2O8 and Ba3Cr2O8 are insulating dimerized antiferromagnets with Cr5+ magnetic ions. These spin-12 ions form hexagonal bilayers with a strong intradimer antiferromagnetic interaction that leads to a singlet ground state and gapped triplet states. We report on the effect on the magnetic properties of Sr3Cr2O8 by introducing chemical disorder upon replacing Sr by Ba. Two single crystals of Ba3−xSrxCr2O8 with x=2.9 (3.33% of mixing) and x=2.8 (6.66% of mixing) were grown in a four-mirror-type optical floating-zone furnace. The magnetic properties of these compounds were studied by magnetization measurements. Inelastic neutron-scattering measurements on Ba0.1Sr2.9Cr2O8 were performed in order to determine the interaction constants and the spin gap for x=2.9. The intradimer interaction constant is found to be J0=5.332(2)meV, about 4% smaller than that of pure Sr3Cr2O8, whereas the interdimer exchange interaction Je is smaller by 7%. These results indicate a noticeable change in the magnetic properties by a random substitution effect.