Crystal structure and properties of iron-based spin-chain compound Ba9Fe3Se15

TL;DR

This study reports the synthesis and comprehensive analysis of a new quasi-1D iron selenide compound, Ba9Fe3Se15, revealing its structural, magnetic, and pressure-induced electronic transitions, including metallization and spin state crossover.

Contribution

It introduces a new iron selenide compound with unique structural and pressure-dependent electronic and magnetic properties, expanding understanding of 1D iron chalcogenides.

Findings

Ba9Fe3Se15 has a monoclinic structure with face-sharing FeSe6 chains.

It exhibits insulating behavior with a band gap of ~460 meV at ambient pressure.

High pressure induces metallization and a spin state crossover from high spin to low spin.

Abstract

We report the synthesis of a new quasi one-dimensional (1D) iron selenide. Ba9Fe3Se15 was synthesized at high temperature and high pressure of 5.5 GPa and systematically studied via structural, magnetic and transport measurements at ambient and at high-pressures. Ba9Fe3Se15 crystallizes in a monoclinic structure and consists of face-sharing FeSe6 octahedral chains along the c axis. At ambient pressure it exhibits an insulating behavior with a band gap ~460 meV and undergoes a ferrimagnet-like phase transition at 14 K. Under high pressure, a complete metallization occurs at ~29 GPa, which is accompanied by a spin state crossover from high spin (HS) state to low spin (LS) state. The LS appears for pressures P >36 GPa.