Publication details

Spin-State Crossover Model for the Magnetism of Iron Pnictides

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Year of publication 2013
Type Article in Periodical
Magazine / Source Physical Review Letters
MU Faculty or unit

Central European Institute of Technology

Field Solid matter physics and magnetism
Keywords iron pnictides; quantum magnetism; spin-state crossover
Description We propose a minimal model describing magnetic behavior of Fe-based superconductors. The key ingredient of the model is a dynamical mixing of quasidegenerate spin states of Fe2+ ion by intersite electron hoppings, resulting in an effective local spin Seff. The moments Seff tend to form singlet pairs and may condense into a spin nematic phase due to the emergent biquadratic exchange couplings. The longrange ordered part m of Seff varies widely, 0<=m<=Seff, but magnon spectra are universal and scale with Seff, resolving the puzzle of large but fluctuating Fe moments. Unusual temperature dependences of a local moment and spin susceptibility are also explained.
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