We predict an unconventional magnetic ground state in AyFe1.6Se2 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 N{\'e}el-FM phase, a ferromagnetic arrangement of a "{\it{N{\'e}el cluster}}". The new magnetic phase is metallic, and the BS-AFM to N{\'e}el-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.
@article{arxiv.1108.4322,
title = {Block Spin Magnetic Phase Transition of A$_y$Fe$_{1.6}$Se$_2$ Under High Pressure},
author = {Chao Cao and Minghu Fang and Jianhui Dai},
journal= {arXiv preprint arXiv:1108.4322},
year = {2011}
}
Comments
Submitted version. Typos corrected; modified to comply with the length requirement; figure legends have been replaced to be in consistent with the captions