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Title: Mechanically-induced disorder in CaFe 2As 2: A 57Fe Mössbauer study

57Fe Mössbauer spectroscopy was used to perform a microscopic study on the extremely pressure and strain sensitive compound, CaFe 2As 2, 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 CaFe 2As 2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe 2As 2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe 2As 2 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 valuesmore » of quadrupole shift in the magnetic phase decrease 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:
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:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; Mossbauer spectroscopy; CaFe2As2; magnetism; strain
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1397528