Phase diagrams of Ba(Fe(1-x)TMx)2As2 (TM = Rh, Pd) single crystals

TL;DR

This study investigates how Rh and Pd doping in BaFe2As2 affects its phase transitions and superconductivity, revealing similarities with Co and Ni doping despite differences in electronic shells and structural changes.

Contribution

It provides detailed phase diagrams for Rh and Pd doping, highlighting the similar effects of 3d and 4d transition metal doping on phase transitions and superconductivity.

Findings

Superconductivity forms a dome-like region in phase diagrams.

Rh doping effects are similar to Co doping; Pd to Ni doping.

Transition temperatures are better parameterized by electron count than by structural changes.

Abstract

Single crystalline Ba(Fe(1-x)TMx)2As2 (TM = Rh, Pd) series have been grown and characterized by structural, thermodynamic and transport measurements. These measurements show that the structural/magnetic phase transitions, found in pure BaFe2As2 at 134 K, are suppressed monotonically by the doping and that superconductivity can be stablized over a dome-like region. Temperature-composition (T-x) phase diagrams based on electrical transport and magnetization measurements are constructed and compared to those of the Ba(Fe(1-x)TMx)2As2 (TM = Co, Ni) series. Despite the generic difference between 3d and 4d shells and the specific, conspicuous differences in the changes to the unit cell parameters, the effects of Rh doping are exceptionally similar to the effects of Co doping and the effects of Pd doping are exceptionally similar to the effects of Ni doping. These data show that whereas the structural / antiferromagnetic phase transition temperatures can be parameterized by x and the superconducting transition temperature can be parameterized by some combination of x and e, the number of extra electrons associated with the TM doping, the transition temperatures of 3d- and 4d- doped BaFe2As2 can not be simply parameterized by the changes in the unit cell dimensions or their ratios.