Robust block magnetism in the spin ladder compound BaFe$_2$Se$_3$ under hydrostatic pressure

TL;DR

This study investigates the magnetic and structural behavior of BaFe$_2$Se$_3$ under hydrostatic pressure, revealing a structural phase transition and persistent block magnetism, providing insights into pressure-induced phenomena in quasi-one-dimensional iron-based compounds.

Contribution

It provides the first detailed high-pressure analysis of BaFe$_2$Se$_3$, showing structural transition and sustained magnetism, advancing understanding of pressure effects in spin-ladder iron-based materials.

Findings

Structural phase transition at ~3.7 GPa.

Persistence of block magnetism at high pressures.

Rapid decrease of magnetic transition temperature near potential superconductivity.

Abstract

The majority of the iron-based superconductors (FeSCs) exhibit a two-dimensional square lattice structure. Recent reports of pressure-induced superconductivity in the spin-ladder system, BaFe$_2$X$_3$ (X =S,Se), introduce a quasi-one-dimensional prototype and an insulating parent compound to the FeSCs. Here we report X-ray, neutron diffraction and muon spin relaxation experiments on BaFe$_2$Se$_3$ under hydrostatic pressure to investigate its magnetic and structural properties across the pressure-temperature phase diagram. A structural phase transition was identified at a pressure of 3.7(3) GPa. Neutron diffraction measurements at 6.8(3) GPa and 120 K show that the block magnetism persists even at these high pressures. A steady increase and then fast drop of the magnetic transition temperature $T\rm_N$ and greatly reduced moment above the pressure $P_s$ indicate potentially rich and competing phases close to the superconducting phase in this ladder system.