Temperature and composition phase diagram in the iron-based ladder compounds Ba1-xCsxFe2Se3

TL;DR

This study maps the temperature and composition phase diagram of iron-based ladder compounds (Ba,Cs)Fe$_2$Se$_3$, revealing how magnetic structures and electrical properties evolve with doping, and identifying new magnetic phases.

Contribution

It provides the first detailed phase diagram of (Ba,Cs)Fe$_2$Se$_3$ compounds, highlighting the suppression of block magnetism and emergence of new magnetic structures with doping.

Findings

Block magnetism in BaFe$_2$Se$_3$ is suppressed by Cs doping.

Stripe magnetism in CsFe$_2$Se$_3$ is robust against Ba doping.

Intermediate compositions exhibit a new magnetic structure similar to stripe magnetism.

Abstract

We investigated the iron-based ladder compounds (Ba,Cs)Fe$_2$Se$_3$. Their parent compounds, BaFe$_2$Se$_3$ and CsFe$_2$Se$_3$, have different space groups, formal valences of Fe and magnetic structures. Electrical resistivity, specific heat, magnetic susceptibility, X-ray diffraction and powder neutron diffraction measurements were conducted to obtain temperature and composition phase diagram of this system. Block magnetism observed in BaFe$_2$Se$_3$ is drastically suppressed with Cs doping. In contrast, stripe magnetism observed in CsFe$_2$Se$_3$ is not so fragile against Ba doping. New type of magnetic structure appears in intermediate compositions, which is similar to stripe magnetism of CsFe$_2$Se$_3$, but inter-ladder spin configuration is different. Intermediate compounds show insulating behavior, nevertheless finite $T$-linear contribution in specific heat was obtained at low temperatures.