Effects of transition metal doping in MgB${}_2$ superconductor

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 $T_{\mathrm{c}}$: d$T_{\mathrm{c}}$/d$x$ is the largest (= - 159 K) in the Mn-doped sample. We have found Zn-substitution increases $T_{\mathrm{c}}$ ($\Delta T_{\mathrm{c}}\approx$ 0.2 K at x=0.03), perhaps due to the enhanced density of state near the Fermi level.

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