Effect of Molybdenum 4d Hole Substitution in BaFe2As2

TL;DR

This study explores the effects of molybdenum hole doping in BaFe2As2 crystals, revealing how Mo substitution influences magnetic, structural, and electronic properties, and identifying a potential new transition related to doping.

Contribution

First report of hole doping in BaFe2As2 using 4d element Mo, analyzing its impact on phase transitions and electronic properties compared to other dopants.

Findings

Mo doping suppresses magnetic transition temperature similarly to Cr doping.

Cell volume expands by ~1% with Mo doping.

A new low-temperature transition T* is observed, possibly related to superconductivity or magnetic effects.

Abstract

We investigate the thermodynamic and transport properties of molybdenum-doped BaFe2As2 (122) crystals, the first report of hole doping using a 4d element. The chemical substitution of Mo in place of Fe is possible up to ~ 7%. For Ba(Fe1-xMox)2As2, the suppression rate of the magnetic transition temperature with x is the same as in 3d Cr-doped 122 and is independent of the unit cell changes. This illustrates that temperature-composition phase diagram for hole-doped 122 can be simply parameterized by x, similar to the electron-doped 122 systems found in literature. Compared to 122 with a coupled antiferromagnetic order (TN) and orthorhombic structural transition (To) at ~ 132 K, 1.3% Mo-doped 122 (x = 0.013) gives TN = To = 125(1) K according to neutron diffraction results and features in specific heat, magnetic susceptibility and electrical resistivity. The cell volume expands by ~ 1% with maximum Mo-doping and TN is reduced to ~ 90 K. There is a new T* feature that is identified for lightly Cr- or Mo-doped (< 3%) 122 crystals, which is x dependent. This low-temperature transition may be a trace of superconductivity or it may have another electronic or magnetic origin.