Elastic behaviour of strontium-doped lanthanum calcium manganites in the vicinity of TC

Effects of Cd2+ substitution on elastic properties and step-like anomalies in Tl0.9Bi0.1Sr1.8Yb0.2Ca1−Cd Cu1.99Fe0.01o7− superconductors

“…The excellent fitting achieved strongly suggests that the elastic anomaly is due to a phase transition that introduces strain in the system as temperature was lowered. Our results are in agreement to a previous report on step-like anomalies found in La 0.67 Ca 0.33 À x Sr x MnO 3 manganites systems where similar step-like elastic anomalies were found to be associated with a Landau-type phase transition [39]. In the present work, as we have suggested, the phase transition may involve ordering of oxygen in Tl-O planes.…”

Elastic moduli and step-like elastic anomalies in Ce-substituted Tl0.9Bi0.1Sr2−xCexCa0.9Y0.1Cu1.99Fe0.01O7−δ(x= 0–0.20) superconductors

“…[23,32] Based on this model, the free-energy equation that introduces the coupling of the order parameter Q to the strain e using linear order terms like eQ was applied. [23] Therefore, in our present work, the Landau free-energy equation was fitted to the temperature dependence of C L for Tl 0.9 Bi 0.1 Sr 2¡x Ce x Ca 0.9 Y 0.1 Cu 1.99 Fe 0.01 O 7¡d for (x D 0, 0.10 and 0.2) samples. From the Landau treatment, the relationship between the elastic modulus C L and the temperature T both below and above T A can be expressed as follows:…”

“…Application of the model for La 0.67 Ca 0.33¡x Sr x MnO 3 manganites has shown that the elastic anomaly observed fitted well to the model indicating a phase transition. [23] In superconductor materials, the Landau model was previously used to explain the transition of a material from normal to superconducting state. Thus, considering the above, it is interesting to apply the Landau model to investigate the step-like anomaly and effect of Ce substitution on the anomaly in superconducting Tl 0.9 Bi 0.1 Sr 2¡x Ce x Ca 0.9 Y 0.1 Cu 1.99 Fe 0.01 O 7¡d .…”

Effect of pb substitution on structural and electrical transport of La0.7Ca0.3−xPbxMnO3 (0≤x≤0.3) manganites

“…A-site doping can be strongly influenced by the average ionic radius of the A-site (o r A 4 ), which exhibits a close relation between the bending of the Mn-O-Mn bond angle and the narrowing of the electronic band width [12]. Many authors have also reported the structural properties and transport mechanism on La 0.7 Sr x Ca 0.3 À x MnO 3 Contents lists available at ScienceDirect systems [21][22][23][24] and they observed T C is strongly suppressed when the difference in ionic radius between two cations at A sites is large. At a composition x ¼0.15 (amount of Ca approximately equals amount of Sr), which is of our interest, there is structural phase transition from the orthorhombic (Pbnm) phase to the rhombohedral (R c 3 ) or monoclinic (Pc/2) one [17,19].…”