Two-dimensional magnetism in the pnictide superconductor parent material SrFeAsF probed by muon-spin relaxation

TL;DR

This study investigates the magnetic properties of SrFeAsF, a parent compound of iron-based superconductors, revealing its layered magnetic transitions and weaker interlayer magnetic exchange compared to similar materials.

Contribution

First muon-spin relaxation study of SrFeAsF showing its magnetic transition characteristics and comparison with related compounds.

Findings

Magnetic transition at 120 K and structural transition at 175 K.

Weak interlayer magnetic exchange inferred from muon oscillation behavior.

No entropy anomaly at magnetic transition, indicating decoupled magnetic and structural changes.

Abstract

We report muon-spin relaxation measurements on SrFeAsF, which is the parent compound of a newly discovered iron-arsenic-fluoride based series of superconducting materials. We find that this material has very similar magnetic properties to LaFeAsO, such as separated magnetic and structural transitions (TN = 120 K, Ts = 175 K), contrasting with SrFe2As2 where they are coincident. The muon oscillation frequencies fall away very sharply at TN, which suggests that the magnetic exchange between the layers is weaker than in comparable oxypnictide compounds. This is consistent with our specific heat measurements, which find that the entropy change S = 0.05 J/mol/K largely occurs at the structural transition and there is no anomaly at TN.