Temperature and composition phase diagram in the iron-based ladder compoundsBa1−xCsxFe2Se3

Abstract

We investigated the iron-based ladder compounds (Ba,$\mathrm{Cs}){\mathrm{Fe}}_{2}{\mathrm{Se}}_{3}$. Their parent compounds ${\mathrm{BaFe}}_{2}{\mathrm{Se}}_{3}$ and ${\mathrm{CsFe}}_{2}{\mathrm{Se}}_{3}$ 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 a temperature and composition phase diagram of this system. Block magnetism observed in ${\mathrm{BaFe}}_{2}{\mathrm{Se}}_{3}$ is drastically suppressed with Cs doping. In contrast, stripe magnetism observed in ${\mathrm{CsFe}}_{2}{\mathrm{Se}}_{3}$ is not so fragile against Ba doping. A new type of magnetic structure appears in intermediate compositions, which is similar to stripe magnetism of ${\mathrm{CsFe}}_{2}{\mathrm{Se}}_{3}$, but interladder spin configuration is different. Intermediate compounds show insulating behavior, nevertheless a finite $T$-linear contribution in specific heat was obtained at low temperatures.