Superconductivity and phase diagrams in 4d- and 5d-metal-doped iron arsenides SrFe_{2-x}M_xAs_2 (M = Rh, Ir, Pd)

TL;DR

This study synthesizes and analyzes superconductors formed by doping SrFe_2As_2 with 4d and 5d transition metals Rh, Ir, and Pd, revealing how doping suppresses antiferromagnetism and induces superconductivity with phase diagrams similar to Co and Ni doping.

Contribution

It provides the first systematic exploration of superconductivity and phase diagrams in SrFe_{2-x}M_xAs_2 with 4d and 5d transition metal doping, highlighting differences in suppression rates and the role of AF order.

Findings

Superconductivity is induced by doping Rh, Ir, and Pd, suppressing antiferromagnetic order.

Phase diagrams are similar to Co and Ni doping but differ in suppression rates.

Superconductivity correlates with AF order suppression, not electron-phonon coupling.

Abstract

By substituting the Fe with the 4d and 5d-transition metals Rh, Ir and Pd in SrFe_2As_2, we have successfully synthesized a series of superconductors SrFe_{2-x}M_xAs_2 (M = Rh, Ir and Pd) and explored the phase diagrams of them. The systematic evolution of the lattice constants indicated that part of the Fe ions were successfully replaced by the transition metals Rh, Ir and Pd. By increasing the doping content of Rh, Ir and Pd, the antiferromagnetic state of the parent phase is suppressed progressively and superconductivity is induced. The general phase diagrams were obtained and found to be similar to the case of doping Co and Ni to the Fe sites. However, the detailed structure of the phase diagram, in terms of how fast to suppress the antiferromagnetic order and induce the superconductivity, varies from one kind of doped element to another. Regarding the close values of the maximum superconducting transition temperatures in doping Co, Rh and Ir which locate actually in the same column in the periodic table of elements but have very different masses, we argue that the superconductivity is intimately related to the suppression of the AF order, rather than the electron-phonon coupling.