Magnetic phase diagram of an extended J1-J2 model on a modulated square lattice and its implications for the antiferromagnetic phase of KyFexSe2

Rong Yu*, Pallab Goswami, Qimiao Si

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Motivated by the experimentally observed √5×√5 iron vacancy order and a block-spin antiferromagnetic phase with large magnetic moment in K0.8Fe1.6Se2, we study the magnetic phase diagram of an extended J1-J2 model on a 15-depleted square lattice with √5×√5 vacancy order, using a classical Monte Carlo analysis. The magnetic phase diagram involves various antiferromagnetically ordered phases, and most of them have higher-order commensuration. We find that the experimentally relevant block-spin state occupies a significant portion of the phase diagram, and we discuss the spin dynamics of this phase using a linear spin-wave analysis. By comparing the calculated magnetization with the experimental values of magnetic moment, we determine the physical parameter regimes corresponding to the block-spin antiferromagnetic phase. Based on our spin-wave calculations in different parameter regimes, we show how spin-wave degeneracy along the high-symmetry directions of the magnetic Brillouin zone can provide information regarding the underlying exchange couplings. We have also analyzed the magnetic phase diagram of a J1-J2 model on two different modulated square lattices relevant to KyFe1.5Se2, which respectively exhibit 14-depleted 2×2 and 4×2 vacancy ordering.

Original languageEnglish (US)
Article number094451
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume84
Issue number9
DOIs
StatePublished - Sep 28 2011

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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