Pressure- and temperature-induced structural phase transitions of CaFe${}_2$As${}_2$ and BaFe${}_2$As${}_2$ studied in the Hund's rule correlation picture

Abstract

With the proposed Hund's rule correlation picture, i.e. the fluctuating Fe local moments with the As-bridged antiferromagnetic superexchange interactions, the exceptional collapsed tetragonal phase and related phase transitions observed in CaFe${}_2$As${}_2$ are well understood. With the same framework, a pressure-temperature phase diagram is predicted for BaFe${}_2$As${}_2$ as well, in which a paramagnetic tetragonal and a collinear antiferromagnetic orthorhombic structures to nonmagnetic tetragonal structure transitions take place around 4-8 GPa and 10-15 GPa respectively, and a nonmagnetic tetragonal to a nonmagnetic collapsed tetragonal structure transition takes place over 26 GPa. Our study helps better understand the complex correlation among crystal structure, magnetism, and electronic structure in pnictides, a precondition to understand the superconductivity in pnictides.

5 pages and 4 figures

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Cited by in corpus (1)

• Electronic and magnetic structures of ternary iron selenides AFe${}_2$Se${}_2$ (A=K, Cs, or Tl)