Damped Soft Phonons and Diffuse Scattering in 40PMN-60PT

Abstract

Using neutron elastic and inelastic scattering and high-energy x-ray diffraction, we present a comparison of 40% Pb(Mg${}_{1/3}$Nb${}_{2/3}$)O${}_3$-60% PbTiO${}_3$ (PMN-60PT) with pure Pb(Mg${}_{1/3}$Nb${}_{2/3}$)O${}_3$ (PMN) and PbTiO${}_3$ (PT). We measure the structural properties of PMN-60PT to be identical to pure PT, however, the lattice dynamics are exactly that previously found in relaxors PMN and PZN. PMN-60PT displays a well-defined macroscopic structural transition from a cubic to tetragonal unit cell at 550 K. The diffuse scattering is shown to be weak indicating that the structural distortion is long-range in PMN-60PT and short-range polar correlations (polar nanoregions) are not present. Even though polar nanoregions are absent, the soft optic mode is short-lived for wavevectors near the zone-centre. Therefore, PMN-60PT displays the same waterfall effect as prototypical relaxors PMN and PZN. We conclude that it is random fields resulting from the intrinsic chemical disorder which is the reason for the broad transverse optic mode observed in PMN and PMN-60PT near the zone centre and not due to the formation of short-ranged polar correlations. Through our comparison of PMN, PMN-60PT, and pure PT, we interpret the dynamic and static properties of the PMN-xPT system in terms of a random field model in which the cubic anisotropy term dominates with increasing doping of PbTiO${}_3$.

13 pages, 13 figures

References in corpus (18)

• Direct observation of the formation of polar nanoregions in Pb(Mg${}_{1/3}$Nb${}_{2/3}$)O${}_3$ using neutron pair distribution function analysis
• Polarized Raman study of the phonon dynamics in Pb(Mg${}_{1/3}$Nb)O${}_3$ crystal
• Electric-field induced phase transitions in rhombohedral PZN-xPT
• Development of Ferroelectric Order in Relaxor (1-x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3
• Ferroelectric Ordering in the Relaxor Pb(Mg1/3Nb2/3)O3 as Evidenced by Low-Temperature Phonon Anomalies
• Origin of the "Waterfall" Effect in Phonon Dispersion of Relaxor Perovskites
• Central mode and soft mode behavior in PbMg1/Nb2/3O3 relaxor ferroelectric
• Universal Static and Dynamic Properties of the Structural Transition in Pb(Zn1/3Nb2/3)O3
• Ground State of Relaxor Ferroelectric $Pb(Z{n}_{1/3}N{b}_{2/3})O_3$
• Random Field Models for Relaxor Ferroelectric Behavior
• Cold neutron scattering study on diffuse and phonon excitations in the relaxor PbMg(1/3)Nb(2/3)O3
• A Universal Phase Diagram for PMN-xPT and PZN-xPT
• Direct evidence of soft mode behavior near the Burns' temperature in PbMg${}_{1/3}$Nb${}_{2/3}$O${}_3$ (PMN) relaxor ferroectric
• Quasi-Elastic Scattering, Random Fields and phonon-coupling effects in PbMg1/3Nb2/3O3
• An Anomalous Phase in the Relaxor Ferroelectric Pb(Zn${}_{1/3}$Nb${}_{2/3}$)O${}_3$
• Strong Influence of the diffuse component on the lattice dynamics in Pb(Mg${}_{1/3}$Nb${}_{2/3}$)O${}_3$
• Far-infrared soft mode behavior in PST thin films
• Investigation of dielectric anomalies at cryogenic temperatures in the (1-x)[Pb(Mg1/3 Nb2/3)O3]-xPbTiO3 system

Cited by in corpus (18)

• Phase instability induced by polar nanoregions in a relaxor ferroelectric system
• The role of random electric fields in relaxors
• A reassessment of the Burns temperature and its relationship to the diffuse scattering, lattice dynamics, and thermal expansion in the relaxor PMN
• Soft phonon columns on the edge of the Brillouin zone in the relaxor PbMg1/3Nb2/3O3
• Competing orders in PZN-xPT and PMN-xPT relaxor ferroelectrics
• Dynamic origin of the morphotropic phase boundary - Soft modes and phase instability in 0.68Pb(Mg1/3Nb2/3O3)-0.32PbTiO3
• Dielectric properties and lattice dynamics of Ca-doped K${}_{0.95}$Li${}_{0.05}$TaO${}_3$
• Evidence for anisotropic polar nanoregions in relaxor PMN: A neutron study of the elastic constants and anomalous TA phonon damping
• A two-component model of the neutron diffuse scattering in the relaxor ferroelectric PZN-4.5%PT
• Response of polar nanoregions in 68%Pb(Mg1/3Nb2/3)O3-32%PbTiO3 to a [001] electric field
• The Structural Phase Transition of the Relaxor Ferroelectric 68%PbMg1/3Nb2/3O3-32%PbTiO3
• Temperature independent diffuse scattering and elastic lattice deformations in relaxor PbMg1/3Nb2/3O3
• Spontaneous decay of a soft optical phonon in the relaxor ferroelectric PbMg${}_{1/3}$Nb${}_{2/3}$O${}_3$
• The effect of local dipole moments on the structure and lattice dynamics of K0.98Li0.02TaO3
• Fluctuating defects in the incipient relaxor K${}_{1-x}$Li${}_x$TaO${}_3$ (x=0.02)
• Electric field effect on short-range polar orders in a relaxor ferroelectric system
• Broadband critical dynamics in disordered lead-based perovskites
• Phonon coupling to dynamic short-range polar order in a relaxor ferroelectric near the morphotropic phase boundary