Two-Magnon Raman Scattering in KNiF3

Abstract

Raman scattering of 5145-Å argon laser radiation by two magnons in the perovskite antiferromagnet KNiF3 has been observed. At low temperature, the spectrum of the scattered light is in excellent agreement with a Green's function theory for a perovskite with S = 1 and nearest-neighbor exchange constant J = (71.0±0.8) cm−1. If the effects of anisotropy (obtained from far-infrared antiferromagnetic resonance measurements) are included, the value of J is changed only slightly, decreasing ≈0.5 cm−1. The line shape and position were also observed as functions of temperature. A comparison is made with similar scattering observed in RbMnF3 (S=52) and in related magnetic Ni2+ fluorides.