Direct observation of the near-surface layer in Pb(Mg_1∕3Nb_2∕3)O₃ using neutron diffraction

Spatially resolved neutron diffraction as a function of crystal depth in Pb(Mg_1∕3Nb_2∕3)O₃ reveals the presence of a distinct near-surface region where a strong distortion in the lattice exists. A dramatic change in both the lattice constant and the Bragg peak intensity as a function of crystal depth is observed to occur in this region over a length scale ∼100 μm. This confirms a previous assertion, based on a comparison between high-energy x rays and neutrons, that such a near surface region exists in the relaxors. Consequences to both single crystal and powder diffraction measurements and previous bulk neutron diffraction measurements on large single crystals are discussed.