Block Spin Magnetic Phase Transition of A_yFe_1.6Se₂ Under High Pressure

2011/08/22 by Chao Cao, Cao, Chao, Minghu Fang +3
Physics and Astronomy · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Superconductivity (cond-mat.supr-con) #cond-mat.mtrl-sci #cond-mat.supr-con

paper · pdf · doi:10.48550/arxiv.1108.4322

Submitted version. Typos corrected; modified to comply with the length requirement; figure legends have been replaced to be in consistent with the captions

arxiv created 2011/08/27 · arxiv updated 2011/08/30

Abstract

We predict an unconventional magnetic ground state in A_yFe_1.6Se₂ with √(5)×√(5) Fe-vacancy superstructure under hydraulic external pressure based on first-principles simulations. While the Fe-vacancy ordering persists up to at least ∼ 12GPa, the magnetic ground state goes at ∼10GPa from the BS-AFM phase to a Néel-FM phase, a ferromagnetic arrangement of a "\itNéel cluster". The new magnetic phase is metallic, and the BS-AFM to Néel-FM phase transition is accompanied by a sizable structural change. The two distinct magnetic phases can be understood within the extended J₁-J₂ Heisenberg model by assuming a pressure-tuned competition between the intrablock and interblock nearest-neighbor couplings of iron moments.

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