Spin-State Crossover Model for the Magnetism of Iron Pnictides

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Authors	CHALOUPKA Jiří KHALIULLIN Giniyat
Year of publication	2013
Type	Article in Periodical
Magazine / Source	Physical Review Letters
MU Faculty or unit	Central European Institute of Technology
Citation
Web	http://prl.aps.org/abstract/PRL/v110/i20/e207205
Doi	http://dx.doi.org/10.1103/PhysRevLett.110.207205
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.
Related projects:	CEITEC - Central European Institute of Technology SYLICA - Synergies of Life and Material Sciences to Create a New Future