Quenched Fe Moment in the Collapsed Tetragonal Phase of Ca$_{1-x}$Pr$_{x}$Fe$_2$As$_2$

TL;DR

This study uses $^{75}$As NMR to investigate the magnetic and structural changes in Pr-doped CaFe$_2$As$_2$, revealing quenched Fe moments and the interplay between structure and magnetism in the collapsed tetragonal phase.

Contribution

It provides new insights into the magnetic behavior and structural transition in Pr-doped CaFe$_2$As$_2$, highlighting the quenched Fe moments in the collapsed tetragonal phase.

Findings

Quenching of Fe local magnetism in the collapsed phase

Evidence of short-range Pr$^{3+}$ moment ordering

Strong interplay between structure and magnetism

Abstract

We report $^{75}$As NMR studies on single crystals of rare-earth doped iron pnictides superconductor Ca$_{1-x}$Pr$_{x}$Fe$_{2}$As$_{2}$ ($x$=0.075 and 0.15). The $^{75}$As spectra show a chemical pressure effect with doping and a first order structure transition to the collapsed tetragonal phase upon cooling. A sharp drop of the Knight shift is seen below the structural transition, whereas $1/T_1$ is strongly enhanced at low-temperatures. These evidences indicate quenching of Fe local magnetism and short-range ordering of Pr$^{3+}$ moment in the collapsed tetragonal phase. The quenched Fe moment through structure collapse suggests a strong interplay of structure and magnetism, which is important for understanding the nature of the collapsed tetragonal phase.