Abstract
We employ the sensitivity of high-energy sidebands on the 1 eV absorption band to temperature and applied magnetic field to investigate the phase transition in Data were collected in steady (45 T) and pulsed (60 T) fields between 4 and 45 K. We use the spectral changes to map the phase diagram and find a temperature-independent phase boundary at which persists above 34 K a kink in near 27 T, and behavior of in the high-field phase with prefactor It is notable that the energy scale of is identical to that of To understand the high-energy sidebands on the 1 eV band in the optical conductivity, we invoke the idea of low-energy excitations coupled with the optically induced charge transfer excitation. The 34 K phase transition is assigned as a crossover between thermal excitation over the on-rung potential barrier above and tunneling through the barrier below and is associated with a change in the on-rung potential, which modifies the low-energy excitation dynamics and may lead to the formation of field-induced ferromagnetic domains above 27 T.
- Received 13 March 2002
DOI:https://doi.org/10.1103/PhysRevB.66.054439
©2002 American Physical Society