Intertwined magnetic and nematic orders in semiconducting KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$

Abstract

Superconductivity in the iron pnictides emerges from metallic parent compounds exhibiting intertwined stripe-type magnetic order and nematic order, with itinerant electrons suggested to be essential for both. Here we use X-ray and neutron scattering to show that a similar intertwined state is realized in semiconducting KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ (K${}_5$Fe${}_4$Ag${}_6$Te${}_{10}$) without itinerant electrons. We find Fe atoms in KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ form isolated $2\times 2$ blocks, separated by nonmagnetic Ag atoms. Long-range magnetic order sets in below $T_{\mathrm{N}}\approx 35$ K, with magnetic moments within the $2\times 2$ Fe blocks ordering into the stripe-type configuration. A nematic order accompanies the magnetic transition, manifest as a structural distortion that breaks the fourfold rotational symmetry of the lattice. The nematic orders in KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ and iron pnictide parent compounds are similar in magnitude and how they relate to the magnetic order, indicating a common origin. Since KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ is a semiconductor without itinerant electrons, this indicates that local-moment magnetic interactions are integral to its magnetic and nematic orders, and such interactions may play a key role in iron-based superconductivity.

supplemental material available upon request, to be published in PRL

References in corpus (11)

• Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems
• Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors
• Magnetic order in BaFe2As2, the parent compound of the FeAs based superconductors in a new structural family
• Strong Correlations and Magnetic Frustration in the High Tc Iron Pnictides
• Theory of Electron Nematic Order in LaOFeAs
• Incommensurate magnetic order in the alpha-Fe(Te,Se) superconductor systems
• Ising and Spin orders in Iron-based Superconductors
• Manifestations of nematic degrees of freedom in the magnetic, elastic, and superconducting properties of the iron pnictides
• Spin reorientation in TlFe1.6Se2 with complete vacancy ordering
• Evolution of the nuclear and magnetic structures of TlFe1.6Se2 with temperature
• Local breaking of four-fold rotational symmetry by short-range magnetic order in heavily overdoped Ba(Fe${}_{1-x}$Cu${}_x$)${}_2$As${}_2$

Cited by in corpus (3)

• Orbital selectivity in electron correlations and superconducting pairing of iron-based superconductors
• Strain-induced spin-nematic state and nematic susceptibility arising from $2\times 2$ Fe clusters in KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$
• Twinning of domains and spin anisotropy in K${}_5$Fe${}_4$Ag${}_6$Te${}_{10}$