Abstract
With infrared spectroscopy we investigated the spin-reorientation transition from an orthorhombic antiferromagnetic (o-AF) to a tetragonal AF (t-AF) phase and the reentrance of the o-AF phase in the superconducting state of underdoped . In agreement with the predicted transition from a single- to a double- AF structure, we found that a distinct spin density wave develops in the t-AF phase. The pair breaking peak of this spin density wave acquires much more low-energy spectral weight than the one in the o-AF state which indicates that it competes more strongly with superconductivity. We also observed additional phonon modes in the t-AF phase which likely arise from a Brillouin-zone folding that is induced by the double- magnetic structure with two Fe sublattices exhibiting different magnitudes of the magnetic moment.
- Received 16 January 2015
DOI:https://doi.org/10.1103/PhysRevLett.115.027003
© 2015 American Physical Society