He-atom-scattering studies of the structure and dynamics of theKMnF3(001) surface and the 186-K phase transition

Polar catastrophe and the structure ofKTa1−xNbxO3surfaces: Resu

“…(2) K + ions bridging pairs of surface oxygens act as independent oscillators, in agreement with calculations by Fritsch and Schröder. [6,34] (3) The bridging K + ions, initially randomly arranged on the KO surface, order into (2×1) and (1×2) domains when the target is thermally cycled to low temperatures, and become disordered again when the target is warmed above 330 K. A schematic illustration of the surface is presented in The KTN (001) surfaces examined in this laboratory contrast sharply with those of KMnF 3 studied by similar HAS experiments [15]. This is likely due to the charged KO and TaO 2 /NbO 2 layers in the KTNs vs the neutral KF and MnF 2 layers in KMnF 3 that are exposed when the respective samples are cleaved.…”

“…[6][7][8] The halforder peaks disappeared from the diffraction pattern when the target was warmed above 330K. [6] In similar HAS diffraction experiments on the fluoride perovskite KMnF 3 [15], Toennies and Vollmer observed much longer-lived metastable peaks flanking the specular peak. These diminished in about 20 days rather than in about an hour as found for the KTNs.…”

“…[11][12][13][14] Our results contrast with those from similar HAS experiments on the fluoride perovskite KMnF 3 . [15] In recent work studying the (100) interface of LaAlO 3 and strontium titanate SrTiO 3 , researchers have found unexpected electrical conduction, magnetism and superconductivity. [11][12][13][14][16][17][18][19][20][21][22][23][24][25] The perovskite structure of LaAlO 3 consists of (100) LaO and AlO 2 layers, which are formally charged +1 and -1, respectively.…”

“…The dispersion curves for KMnF 3 measured in the two high symmetry directions differ from each other, as expected, since the bulk dispersion curves corresponding to these surface azimuths differ. [15] We briefly summarize the HAS experimental results on the KTNs. (1) Repeated He diffraction measurements near the specular reflection peak soon after cleaving KTN samples showed metastable behavior.…”

Helium atom scattering study of the interaction of water with the BaF2(111) surface

“…22 Therefore the description of the experimental setup is brief and restricted to the most essential details.…”