Effects of transition metal doping in MgB$_2$ superconductor

TL;DR

This study investigates how doping MgB₂ with various transition metals affects its superconducting transition temperature, revealing that magnetic dopants suppress it while Zn slightly enhances it, highlighting the role of electronic structure modifications.

Contribution

It systematically examines the effects of different transition metal dopants on MgB₂'s superconductivity, providing new insights into how magnetic and non-magnetic substitutions influence $T_c$.

Findings

Mn doping causes the largest suppression of $T_c$ (-159 K per x).

Zn doping slightly increases $T_c$ by about 0.2 K at x=0.03.

Magnetic ions suppress superconductivity, while Zn enhances it.

Abstract

Effects of chemical substitution of the divalent transition metals has been systematically investigated in Mg$_{1-x}M_x$B$_2$ (x=0.03; M=Mn, Fe, Co, Ni and Zn). Substitution of magnetic ions, i.e., Mn$^{2+}$, Fe$^{2+}$, Co$^{2+}$ and Ni$^{2+}$, for the Mg$^{2+}$ ion suppresses $T_{\rm c}$: d$T_{\rm c}$/d$x$ is the largest (= - 159 K) in the Mn-doped sample. We have found Zn-substitution increases $T_{\rm c}$ ($\Delta T_{\rm c} \approx$ 0.2 K at x=0.03), perhaps due to the enhanced density of state near the Fermi level.