Local disorder studied inSrTiO3at low temperature by EXAFS spectroscopy

Abstract

The temperature dependence of the local distortions in SrTi03 has been studied by EXAFS spectroscopy at the titanium E edge (4982 eV). The oxygen-ion Debye-Wailer factor pro has been determined from 4.5 to 240 K. The antiferrodistortive transition at 105 K is evidenced by a step in this Debye-Waller factor. At about 31 K, a maximum of o o is detected and the EXAFS oscillations due to the first oxygen shell increase. This is the signature of a maximum disorder in the lattice vibrations in this temperature range. A quasiharmonic model with a sinusoidal modulation of the Ti-0 distance cannot account for these observations. The lattice and electronic excitations which could support our data are qualitatively described.

Assessing the feasibility of low temperature XAFS experiments at Indus-2, India: First results

“…The minimum temperature step size, for low temperature-dependent XAFS experiments, is determined to be ΔT ¼ 5 K. We expect the calibration to be as good for metallic samples in general. For insulating samples, adequate temperature accuracy can be attained if thin and uniform samples (on tape/pellets) are sandwiched between the plates of Cu sample holder [5][6]11,25,42]. 1 Following this first report of commissioning low temperature XAFS facility at Indus-2, we plan to pursue lower (o50 K) temperature-XAFS of non-standard samples in the future.…”

“…(ii) XAFS, being element-specific probe, can extract well-resolved structural information around different sites separately [16][17][18][19][20]. Low temperature XAFS experiments have gained impetus over the years, due to the growing importance of understanding short-rangeorder (SRO) changes across magneto-electronic phase transitions that generally occur at low temperature (T c o o300 K) [8,[21][22][23][24][25]. For example, in Ref.…”

Echtzeit-Untersuchungen der ferroelektrischen Phasenumwandlungen in K2SeO4 und SrTiO3 unter dem Einfluss eines elektrischen Feldes

“…Eine vergleichende Studie verschiedener ferroelektrischer Perowskite zeigte einen Zusammenhang zwischen der Verschiebung des Oktaeder-Zentalions u z und der Umwandlungstemperatur T F E [157]. [161] sowie Anomalien der dielektrischen Permittivität und der Schallgeschwindigkeit [162].…”

Quantum paraelectricity: The tunneling between excited levels

“…In particular, T 1 was found to increase with T , from a low temperature (below 3 K) value up to a high temperature one (in the range from 10 K to 30 K). Such crossover seems also observed in a couple of other experiments, and this might indicate the entry into a coherent state [2][3][4][5]. The temperature dependence of T 1 has been tentatively modelled with a hyperbolic tangent, where four parameters were involved [6].…”