Temperature Dependence of the Ferroelectric Mode in KH2PO4

Abstract

Raman-scattering measurements on K${\mathrm{H}}_2$P${\mathrm{O}}_4$ reveal a broad, low-frequency ferroelectric mode which can be represented by a simple damped-harmonic-oscillator function. The resultant characteristic frequency and reciprocal zero-frequency susceptibility approach zero while the damping factor remains constant as $T$ approaches $T_c$ from above. At high $T$, the characteristic frequency approaches ∼99 ${\mathrm{cm}}^{-1\mathrm{}}$ and the linewidth, ∼170 ${\mathrm{cm}}^{-1\mathrm{}}$.