Long range magnetic order in hydroxide layer doped (Li$_{1-x-y}$Fe$_{x}$Mn$_{y}$OD)FeSe

TL;DR

This study demonstrates that Mn doping in (Li$_{1-x-y}$Fe$_{x}$Mn$_{y}$OD)FeSe induces long-range magnetic order below 12 K without disrupting superconductivity, revealing a pathway to magnetic superconductor design.

Contribution

It provides the first direct neutron diffraction evidence of long-range magnetic order in Mn-doped hydroxide-layered FeSe superconductors, showing controlled doping can tune magnetic properties.

Findings

Mn doping enhances magnetization in the superconductor.

Long-range magnetic order observed below 12 K.

Superconductivity remains unaffected by Mn doping.

Abstract

The (Li$_{1-x}$Fe$_{x}$OH)FeSe superconductor has been suspected to exhibit long-range magnetic ordering due to Fe substitution in the LiOH layer. However, no direct observation such as magnetic reflection from neutron diffraction has be reported. Here, we use a chemical design strategy to manipulate the doping level of transition metals in the LiOH layer to tune the magnetic properties of the (Li$_{1-x-y}$Fe$_{x}$Mn$_{y}$OD)FeSe system. We find Mn doping exclusively replaces Li in the hydroxide layer resulting in enhanced magnetization in the (Li$_{0.876}$Fe$_{0.062}$Mn$_{0.062}$OD)FeSe superconductor without significantly altering the superconducting behavior as resolved by magnetic susceptibility and electrical/thermal transport measurements. As a result, long-range magnetic ordering was observed below 12 K with neutron diffraction measurements. This work has implications for the design of magnetic superconductors for the fundamental understanding of superconductivity and magnetism in the iron chalcogenide system as well as exploitation as functional materials for next generation devices.