Lattice and magnetic instabilities in CaFe$_{2}$As$_{2}$
ORAL
Abstract
Neutron diffraction measurements of a high quality single crystal of CaFe$_{2}$As$_{2}$ are reported. A sharp transition was observed between the high temperature tetragonal and low temperature orthorhombic structures at T$_{S}$=172.5 K (on cooling) and 173.5 K (on warming). Concomitant with the structural transition we observe a rapid, but apparently continuous, ordering of the Fe moments, in a commensurate antiferromagnetic structure, with a saturated moment of 0.80(5) \textit{$\mu $}$_{B}$/Fe directed along the orthorhombic a-axis. The hysteresis of the structural transition is 1 K between cooling and warming and is consistent with previous thermodynamic, transport and single crystal x-ray studies. The temperature onset of magnetic ordering shifts rigidly with the structural transition providing clearest evidence to date of the coupling between the structural and magnetic transitions in this material and the broader class of arsenides.
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Authors
S. Nandi
Ames Loboratory, US DOE and Iowa State University
Ames Laboratory/Department of Physics and Astronomy
Alan Goldman
Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA
Ames Laboratory and Iowa State University
Ames Laboratory, US DOE and Iowa State University
Ames Laboratory
Ames Loboratory, US DOE and Iowa State University
Ames Laboratory/Department of Physics and Astronomy
Ames Laboratory, US DOE, Iowa State University, Ames, IA 5001, USA
Dimitri Argyriou
Helmholtz-Zentrum Berlin fur Materialien und Energie
Bachir Ouladdiaf
Institute Laue-Langevin
Tapan Chatterji
Forschungszentrum Julich Outstation at Institute Laue-Langevin
