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Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.67: Poster

Wednesday, March 24, 2010, 14:00–18:00, Poster D1

ESR Studies of the Quantum Spin Dimer System Ba3Cr2O8 — •D. Kamenskyi1, J. Wosnitza1, S.A. Zvyagin1, J. Krzystek2, A.A. Aczel3, H.A. Dabkowska3, and G.M. Luke31Hochfeld-Magnetlabor Dresden, FZ Dresden - Rossendorf, Dresden, Germany — 2National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA — 3McMaster University, Hamilton, Ontario, Canada

Ba3Cr2O8 is a system of three-dimensionally coupled dimers, exhibiting a field-induced phase transition from a quantum-disordered to a long-range antiferromagnetically ordered state at Hc1 = 12.5 T. We report tunable-frequency electron spin resonance (ESR) studies of Ba3Cr2O8 single crystals performed in a frequency range between 50 and 700 GHz in fields up to 25 T (applied along the c axis). Two gaps in the magnetic excitation spectrum, Δ1 = 564 GHz and Δ2 = 400 GHz, were observed directly, confirming the spin-singlet ground state of Ba3Cr2O8 below Hc1. The observation of singlet-triplet ESR transitions, which are normally forbidden in spin-1/2 dimer systems by selection rules, indicates the break-down of the axial symmetry in this compound. Details of the ESR excitation spectrum of Ba3Cr2O8 across different regions of its phase diagram will be discussed.

This work was partly supported by the DFG and EuroMagNET (EU contract No. 228043).

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