Ferroelectric Soft Mode in Pb(Mg1/3Nb2/3)O3

TL;DR

This study used precision Raman scattering to clearly identify the ferroelectric soft mode in Pb(Mg1/3Nb2/3)O3, revealing its temperature-dependent behavior and confirming its role in polarization.

Contribution

First direct observation of the ferroelectric soft mode in PMN using Raman scattering, clarifying its role in polarization behavior.

Findings

Soft mode softens around 200 K

Polarization in PMN is due to the soft mode

Raman scattering effectively isolates the soft mode

Abstract

Ferroelectric soft mode in Pb(Mg1/3Nb2/3)O3 (PMN) has been clearly resolved by precision Raman scattering measurements for the first time. A polarization direction of the incident laser was chosen along [110] in cubic configuration in order to eliminate strong scattering components around 45 cm-1, which always smeared the low-frequency spectra of PMN. The soft mode frequency omega_s (=\sqrt{omega_0^2-gamma^2}) softens around 200 K, where omega_0 and gamma are a harmonic frequency and a damping constant, respectively. The present result evidenced that the origin of the polarizationthe in PMN is the soft mode.