Abstract
We present a comprehensive study of the coupled tetrahedra compound by theory and experiments in external magnetic fields. We report the observation of a longitudinal magnon in Raman scattering in the ordered state close to quantum criticality. We show that the excited tetrahedral-singlet sets the energy scale for the magnetic ordering temperature This energy is determined experimentally. The ordering temperature has an inverse-log dependence on the coupling parameters near quantum criticality.
- Received 28 January 2003
DOI:https://doi.org/10.1103/PhysRevB.67.174405
©2003 American Physical Society