Persistent Magnetism in Silver-doped BaFe2As2 Crystals

TL;DR

This study explores how silver doping in BaFe2As2 crystals affects their magnetic and structural properties, revealing persistent magnetism and unique physical traits, with theoretical insights into scattering effects preventing superconductivity.

Contribution

It provides the first detailed investigation of silver doping effects in BaFe2As2, highlighting persistent magnetism and unusual physical features distinct from other transition-metal dopants.

Findings

Ag doping reduces TN and TS without splitting, unlike other dopants.

Magnetism remains stable at higher doping levels, showing persistence.

Theoretical calculations indicate strong scattering but minimal magnetic disruption.

Abstract

We investigate the thermodynamic and transport properties of silver-substituted BaFe2As2 (122) crystals, up to ~4.5%. Similar to other transition-metal substitutions in 122, Ag diminishes the antiferromagnetic (TN) and structural (TS) transition temperatures, but unlike other electron-doped 122s, TN and TS coincide without splitting. Although magnetism drops precipitously to TN = 84 K at doping x = 0.029, it only weakly changes above this x, settling at TN = 80 K at x = 0.045. Compared to this persistent magnetism in Ag-122, doping other group 11 elements of either Cu or Au in 122 diminished TN and induced superconductivity near TC = 2 K at x = 0.044 or 0.031, respectively. Ag-122 crystals show reflective surfaces with surprising thicker cross sections for x >= 0.019, the appearance that is in contrast to the typical thin stacked layered feature seen in all other flux-grown x122 and lower Ag-122. This physical trait may be a manifest of intrinsic weak changes in c-lattice and TN. Our theoretical calculations suggest that Ag doping produces strong electronic scattering and yet a relatively small disruption of the magnetic state, both of which preclude superconductivity in this system.