Structural phase transition and superlattice misfit strain of RFeAsO (R=La, Pr, Nd, Sm)

Gabriele Ciasca, A Ricci, N Poccia, B Joseph, L Barba, G Arrighetti, J Yan, Rw Mccallum, Ta Lograsso, Nd Zhigadlo, J Karpinski, A. Bianconi

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

The tetragonal-to-orthorhombic structural phase transition (SPT) in LaFeAsO (La-1111) and SmFeAsO (Sm-1111) single crystals measured by high-resolution x-ray diffraction is found to be sharp while the RFeAsO (R=La, Nd, Pr, Sm) polycrystalline samples show a broad continuous SPT. Comparing the polycrystalline and the single-crystal 1111 samples, the critical exponents of the SPT are found to be the same while the correlation length critical exponents are found to be very different. These results imply that the lattice fluctuations in 1111 systems change in samples with different surface to volume ratio that is assigned to the relieve of the temperature-dependent superlattice misfit strain between active iron layers and the spacer layers in 1111 systems. This phenomenon that is missing in the AFe2As2 (A=Ca, Sr, Ba) “122” systems, with the same electronic structure but different for the thickness and the elastic constant of the spacer layers, is related with the different maximum superconducting transition temperature in the 1111 (55 K) versus 122 (35 K) systems and implies the surface reconstruction in 1111 single crystals.
Original languageEnglish
Pages (from-to)144507-1-144507-5
Number of pages5
JournalPHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS
Volume82
DOIs
Publication statusPublished - 2010

Keywords

  • phase transition, strain

Fingerprint

Dive into the research topics of 'Structural phase transition and superlattice misfit strain of RFeAsO (R=La, Pr, Nd, Sm)'. Together they form a unique fingerprint.

Cite this