Superconductivity above 50 K in Tb$_{1-x}$Th$_{x}$FeAsO

TL;DR

This study reports the synthesis of a new lanthanide iron arsenide superconductor, Tb$_{1-x}$Th$_{x}$FeAsO, achieving superconductivity above 50 K through Th doping, with detailed insights into its magnetic and electronic properties.

Contribution

First demonstration of superconductivity above 50 K in Tb-based LnFeAsO via Th doping, expanding the family of high-temperature iron-based superconductors.

Findings

Superconductivity with $T_c$ up to 52 K was achieved.

Th doping suppresses magnetic and structural anomalies.

Charge carriers are electron-like, with enhanced thermopower in doped samples.

Abstract

We have successfully synthesized one member of LnFeAsO (Ln stands for lanthanides) with Ln=Tb. By partial substitution of Tb$^{3+}$ by Th$^{4+}$, superconductivity with onset $T_{c}$ up to 52 K was observed. In the undoped parent compound, the magnetic moments of Tb$^{3+}$ ions order antiferromagnetically (AFM) at $T_N$ of 2.5 K, and there exists an anomaly in the resistivity at $T^*$ of about 124 K which corresponds to the structural phase transition and/or AFM ordering of magnetic moments of Fe$^{2+}$ ions. This anomaly is severely suppressed by Th doping, similar to the cases of F doped LnFeAsO series. Thermopower measurements show that the charge carrier is electron-like for both undoped and Th doped compounds, and enhanced thermopower in Th doped samples was observed.