Field Cooled and Zero Field CooledPb207NMR and the Local Structure of RelaxorPb

Abstract

An isotropic 207Pb NMR spectrum corresponding to the glassy matrix with spherical shell type Pb shifts from the cubic sites, as well as an anisotropic spectral component corresponding to polar nanoclusters with a Pb shift parallel to the [111] direction, have been observed in a PbMg(1/3)Nb(2/3)O3 (PMN) single crystal. This represents a microscopic confirmation of the model of relaxors first proposed by Burns and Dacol. A sudden increase in the intensity of the anisotropic cluster line is seen for electric fields larger than the critical field around 210 K. This demonstrates the occurrence of an orientational percolation type transition to the field-induced ferroelectric phase with about 50% of the Pb nuclei still remaining in the spherical glass matrix. A similar though smaller increase of the intensity of this line is also seen in the zero field cooled data, demonstrating that relaxor PMN is an incipient ferroelectric.

Phonon localization drives polar nanoregions in a relaxor ferroelectric

“…Burns and Dacol 6 proposed polar nanoregions PNRs and the upper temperature of their stability range, the Burns temperature (T d ), to explain changes in the optical index of refraction and the onset of relaxor behaviour, which occurs several hundred degrees above the Curie temperature, T C . The existence of PNRs has been supported by neutron scattering 7 , nuclear magnetic resonance 8 and piezoresponse force microscopy 9 , but cold-neutron diffuse scattering 10 and dynamical pair distribution function 11 experiments indicate that PNRs fluctuate at T d and do not become static until below an intermediate temperature between T C and T d . Bosak et al 12 did threedimensional (3D) mappings of the PNR diffuse scattering and found that they could be described in terms of transverse-wavelike distortions.…”

Neutron and x-ray diffraction study of cubic [111] field-cooledPb(Mg1∕3Nb2∕3)Stock1, Xu2, Gehring3 et al. 2007Phys. Rev. B593462View full textAdd to dashboardCite

“…7 However, NMR measurements have shown that it is difficult to associate this with the presence of a longranged ferroelectric ground state as two components are measured in the NMR line shape and at least half of the crystal remains in a disordered state. 8 Dielectric measurements have found the presence of a frozen glassy state at low temperatures and have led to theories of random bond and field effects in analogy to the case of spin glasses. [9][10][11][12] Recent neutron and x-ray scattering studies conducted on PMN and PZN in zero field have found no long-range structural distortion in the bulk at low temperatures.…”

Kinetics and thermodynamics of the ferroelectric transitions in PbMg1/3Nb2/3O3 and PbMg1/3Nb2/3O3-12% PbTiO3 crystals

“…Each rapid step covers essentially the whole region in which the field is applied. These optical images do not resolve, however, whether the two steps involve different regions on the few-nanometer scale [8][9][10] of the intrinsic relaxor heterogeneity. Fig.…”

“…[3][4][5][6][7] Even in the FE state, a substantial fraction of the material can remain disordered, with FE nanoregions imbedded in a more disordered glassy matrix, 8,9 as expected theoretically for similar materials. 10 In PMN-12%PT a FE state has been shown to be more stable than the unpolarized state below a transition temperature even when the electric field E ¼ 0, but results on the phase stability in pure PMN were less definite.…”