The effect of local dipole moments on the structure and lattice dynamics of K0.98Li0.02TaO3

Abstract

We present high energy x-ray (67 keV) and neutron scattering measurements on a single crystal of K${}_{1-x}$Li${}_x$TaO${}_3$ for which the Li content ($x=0.02$) is less than $x_c=0.022$, the critical value below which no structural phase transitions have been reported in zero field. While the crystal lattice does remain cubic down to T=10 K under both zero-field and field-cooled ($E\le 4$ kV/cm) conditions, indications of crystal symmetry lowering are seen at $T_C=63$ K where the Bragg peak intensity changes significantly. A strong and frequency-dependent dielectric permittivity is observed at ambient pressure, a defining characteristic of relaxors. However an extensive search for static polar nanoregions, which is also widely associated with relaxor materials, detected no evidence of elastic neutron diffuse scattering between 300 K and 10 K. Neutron inelastic scattering methods were used to characterize the transverse acoustic and optic phonons (TA1 and TO1 modes) near the (200) and (002) Bragg peaks. The zone center TO1 mode softens monotonically with cooling but never reaches zero energy in either zero field or in external electric fields of up to 4 kV/cm. These results are consistent with the behavior expected for a dipolar glass in which the local polar moments are frozen and exhibit no long-range order at low temperatures.

arXiv comment7 pages, 7 figures

References in corpus (12)

• A Neutron Elastic Diffuse Scattering Study of PMN
• Neutron Diffuse Scattering from Polar Nanoregions in the Relaxor Pb(Mg1/3Nb2/3)O3
• Soft Mode Dynamics Above and Below the Burns Temperature in the Relaxor Pb(Mg_1/3Nb_2/3)O_3
• Soft Phonon Anomalies in the Relaxor Ferroelectric Pb(Zn_1/3Nb_2/3)_0.92Ti_0.08O_3
• Universal Static and Dynamic Properties of the Structural Transition in Pb(Zn1/3Nb2/3)O3
• Dynamical effects of the nanometer-sized polarized domains in Pb(Zn1/3Nb2/3)O3
• Cold neutron scattering study on diffuse and phonon excitations in the relaxor PbMg(1/3)Nb(2/3)O3
• Damped Soft Phonons and Diffuse Scattering in 40PMN-60PT
• Strong Influence of the diffuse component on the lattice dynamics in Pb(Mg${}_{1/3}$Nb${}_{2/3}$)O${}_3$
• Disorder and relaxation mode in the lattice dynamics of PbMg${}_{1/3}$Nb${}_{2/3}$O${}_3$ relaxor ferroelectric
• Low energy phonon spectrum and its parameterization in pure KTaO3 under 80 K
• Dielectric properties and lattice dynamics of Ca-doped K${}_{0.95}$Li${}_{0.05}$TaO${}_3$

Cited by in corpus (2)

• Competing orders in PZN-xPT and PMN-xPT relaxor ferroelectrics
• Fluctuating defects in the incipient relaxor K${}_{1-x}$Li${}_x$TaO${}_3$ (x=0.02)