Abstract
We employ a combination of pulsed- and continuous-wave polarized terahertz spectroscopy techniques to probe temperature-dependent spin waves in the antiferromagnet . Our optical data span 1.6–467 K and reveal a conspicuous spin reorientation between 110 and 170 K, during which the lower-energy mode softens completely. Complementary inelastic neutron scattering reveals that the frequencies of the optically excited spin waves are consistent with a temperature-variable spin gap in the low-energy spin-wave dispersion of . The result links the temperature dependence of the spin waves to a dynamic in-plane anisotropy. The magnetic anisotropy is calculated based on the results of the optical measurements. The change observed in the anisotropy energy along the and crystal axes suggests that the spin reorientation evident in is driven by temperature-dependent in-plane anisotropy.
1 More- Received 24 May 2014
- Revised 27 July 2014
DOI:https://doi.org/10.1103/PhysRevB.90.054413
©2014 American Physical Society