Antiferromagnetic order in Ca$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$ observed by $^{75}$As NMR

TL;DR

This study uses $^{75}$As NMR to identify antiferromagnetic order in Ca$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$, revealing a phase transition around 100K with nonuniform magnetic ordering similar to other iron arsenide compounds.

Contribution

First NMR investigation of antiferromagnetic order in Ca$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$, showing a discontinuous phase transition and striped AF order.

Findings

AF transition occurs near 100K

Stripe AF order evidenced by NMR lineshape

Transition likely coincides with structural change

Abstract

$^{75}$As nuclear magnetic resonance (NMR) measurements carried out on underdoped, non-superconducting Ca$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$ reveal physical properties that are similar but not identical to the 122 superconductor parent compounds such as BaFe$_2$As$_2$. Results from the single crystal study indicate a phase transition to an antiferromagnetic (AF) state on cooling through T~100K, albeit nonuniformly. Specifically, the NMR lineshape reflects the presence of staggered hyperfine fields on the As sites associated with a striped AF order. The variation of the internal hyperfine field with temperature suggests that the phase transition to the AF state is discontinuous, and therefore likely coincident with the structural transition inferred from transport experiments.