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Title: Mechanically-induced disorder in CaFe2As2: A 57Fe Mössbauer study

57Fe Mössbauer spectroscopy was used to perform a microscopic study on the extremely pressure and strain sensitive compound, CaFe2As2, with different degrees of strain introduced by grinding and annealing. At the base temperature, in the antiferromagnetic/orthorhombic phase, compared to a sharp sextet Mössbauer spectrum of single crystal CaFe2As2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe2As2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe2As2 can be inhomogeneously suppressed by the grinding induced strain to such an extent that the antiferromagnetic order in parts of the grains forming the powdered sample remain absent all the way down to 4.6 K. However, strain has almost no effect on the temperature dependent hyperfine magnetic field in the grains with magnetic order. Additional electronic and asymmetry information was obtained from the isomer shift and quadrupole splitting. Similar isomer shift values in the magnetic phase for samples with different degrees of strain, indicate that the stain does not bring any significant variation of the electronic density at 57Fe nucleus position. As a result, the absolute values of quadrupole shift in the magnetic phase decreasemore » and approach zero with increasing degrees of strain, indicating that the strain reduces the average lattice asymmetry at Fe atom position.« less
 [1] ;  [2] ;  [2] ;  [2]
  1. Iowa State Univ., Ames, IA (United States); Lanzhou Univ., Gansu Province (China)
  2. Iowa State Univ., Ames, IA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0925-8388; PII: S0925838815313840
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Alloys and Compounds
Additional Journal Information:
Journal Volume: 657; Journal Issue: C; Journal ID: ISSN 0925-8388
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
Country of Publication:
United States
36 MATERIALS SCIENCE Mossbauer spectroscopy; CaFe2As2; magnetism; strain