Enhanced superconductivity in Ti1−xMnx alloys through Mn doping

Abstract

The magnetic element Mn is generally supposed to be harmful to superconductivity. However, the superconducting transition temperature of Ti1−xMnx can be enhanced from 0.4 K (elemental titanium) to about 2.1–2.8 K by doping Mn to the system. Here, we carry out systematic studies on the superconductivity and normal state properties of Ti1−xMnx alloys. With the increase of Mn doping in Ti1−xMnx, we find that the system transforms from hexagonal α phase (P63/mmc) to cubic β phase (Im3¯m), and the superconducting property changes from filamentary to bulk superconductivity. Thus we argue that the superconductivity in the α phase with dilute Mn doping is not intrinsic; it may be induced by the residual β phase embedded in the α phase. Moreover, in Ti0.88Mn0.12, we find a positive Hall coefficient with a significant reduction of charge-carrier density, which is in contrast to pure Ti where the Hall coefficient is negative. The specific-heat data of Ti1−xMnx with x=0.12 can be described by the model of s-wave symmetry with a fully opened gap of 0.37 meV. Transport measurements show that it is a type-II superconductor with a relatively large value of Wilson ratio (RW=3.1) in the normal state, which suggests a moderate electron correlation in Ti1−xMnx with the β phase. The positive correlation between magnetic susceptibility and temperature, and the sudden drop of effective magnetic moment in Ti1−xMnx with x=0.12 may suggest that the material shows a signature of the existence of spin fluctuations.

Source-reported materials — not catalogue approval

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