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Title: Suppression of the Structural Phase Transition and Lattice Softening in Slightly Underdoped Ba1−xKxFe2As2 with Electronic Phase Separation

Abstract

We present x-ray powder diffraction (XRPD) and neutron-diffraction measurements on the slightly underdoped iron-pnictide superconductor Ba1-xKxFe2As2, Tc=32 K. Below the magnetic-transition temperature Tm=70 K, both techniques show an additional broadening of the nuclear Bragg peaks, suggesting a weak structural phase transition. However, macroscopically the system does not break its tetragonal symmetry down to 15 K. Instead, XRPD patterns at low temperature reveal an increase in the anisotropic microstrain proportionally in all directions. We associate this effect with the electronic phase separation previously observed in the same material and with the effect of lattice softening below the magnetic phase transition. We employ density-functional theory to evaluate the distribution of atomic positions in the presence of dopant atoms both in the normal and magnetic states and to quantify the lattice softening, showing that it can account for a major part of the observed increase in the microstrain.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
980587
Report Number(s):
BNL-93505-2010-JA
Journal ID: ISSN 1098-0121; TRN: US201015%%1972
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 79; Journal ID: ISSN 1098-0121
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; BRAGG CURVE; DIFFRACTION; DISTRIBUTION; INHIBITION; MATERIALS; NEUTRON DIFFRACTION; POWDERS; SUPERCONDUCTORS; SYMMETRY; TEMPERATURE RANGE 0065-0273 K; national synchrotron light source

Citation Formats

Inosov, D, Leineweber, A, Yang, X, Park, J, Christensen, N, Dinnebier, R, Sun, G, Niedermayer, C, Haug, H, and et. al. Suppression of the Structural Phase Transition and Lattice Softening in Slightly Underdoped Ba1−xKxFe2As2 with Electronic Phase Separation. United States: N. p., 2009. Web. doi:10.1103/PhysRevB.79.224503.
Inosov, D, Leineweber, A, Yang, X, Park, J, Christensen, N, Dinnebier, R, Sun, G, Niedermayer, C, Haug, H, & et. al. Suppression of the Structural Phase Transition and Lattice Softening in Slightly Underdoped Ba1−xKxFe2As2 with Electronic Phase Separation. United States. doi:10.1103/PhysRevB.79.224503.
Inosov, D, Leineweber, A, Yang, X, Park, J, Christensen, N, Dinnebier, R, Sun, G, Niedermayer, C, Haug, H, and et. al. Thu . "Suppression of the Structural Phase Transition and Lattice Softening in Slightly Underdoped Ba1−xKxFe2As2 with Electronic Phase Separation". United States. doi:10.1103/PhysRevB.79.224503.
@article{osti_980587,
title = {Suppression of the Structural Phase Transition and Lattice Softening in Slightly Underdoped Ba1−xKxFe2As2 with Electronic Phase Separation},
author = {Inosov, D and Leineweber, A and Yang, X and Park, J and Christensen, N and Dinnebier, R and Sun, G and Niedermayer, C and Haug, H and et. al.},
abstractNote = {We present x-ray powder diffraction (XRPD) and neutron-diffraction measurements on the slightly underdoped iron-pnictide superconductor Ba1-xKxFe2As2, Tc=32 K. Below the magnetic-transition temperature Tm=70 K, both techniques show an additional broadening of the nuclear Bragg peaks, suggesting a weak structural phase transition. However, macroscopically the system does not break its tetragonal symmetry down to 15 K. Instead, XRPD patterns at low temperature reveal an increase in the anisotropic microstrain proportionally in all directions. We associate this effect with the electronic phase separation previously observed in the same material and with the effect of lattice softening below the magnetic phase transition. We employ density-functional theory to evaluate the distribution of atomic positions in the presence of dopant atoms both in the normal and magnetic states and to quantify the lattice softening, showing that it can account for a major part of the observed increase in the microstrain.},
doi = {10.1103/PhysRevB.79.224503},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = ,
volume = 79,
place = {United States},
year = {2009},
month = {1}
}