Effect of single-ion anisotropy on two-magnon Raman spectra of Heisenberg ferromagnets

Publisher Website
Google Scholar
Abstract
Two‐magnon Raman spectra exhibit magnon pairing effects for zero total wavevector (K↘=O) as resonances within, or bound states below, the two‐magnon continuum. Calculations of the appropriate spectral function describing the excitation of two spin deviations on one site are reported for nearest neighbor s.c. and f.c.c. Heisenberg ferromagnets with single‐ion anisotropy as a variable parameter. Since our approach probes effects both within and outside the continuum, the results go considerably beyond conventional bound state analyses. As the relative strength (D/J) of the single‐ion anisotropy to the exchange is increased, the resonance found in the isotropic case moves lower in the two‐magnon band, which itself is elevated by the anisotropy gap. The line profile varies in a complicated fashion, narrowing at first, then broadening before weakening as the single‐ion resonance moves out of the bottom of the band to become a bound state. The single‐ion bound state has been located through the real part of the spectral function and is confirmed by a sum rule analysis.

This publication has 0 references indexed in Scilit: