Critical current behavior of superconducting MoN andMo3Sb7microfibers

We present the transport and critical current measurements on carbon microfibers coated with 40-nm of polycrystalline $\ensuremath{\delta}\text{-MoN}$ and on carbon microfibers coated with 160 nm of ${\text{Mo}}_{3}{\text{Sb}}_{7}$. In each case the coatings where synthesized directly onto the $6\text{\ensuremath{-}}\ensuremath{\mu}\text{m}$ diameter carbon fibers. The superconducting transition temperature of the MoN microfibers was ${T}_{c}\ensuremath{\sim}13.1\text{ }\text{K}$, which is the highest temperature reported in any thin film form and is higher than what was reported for stoichiometric $\ensuremath{\delta}\text{-MoN}$, produced by high pressure synthesis. The transition temperature of the ${\text{Mo}}_{3}{\text{Sb}}_{7}$-coated microfibers ${T}_{c}=7.5\text{ }\text{K}$ was significantly higher than that observed in powder samples. Near the transition temperature ${T}_{c}$, the critical current density ${J}_{c}$ for both systems was well described by the power-law form ${[1\ensuremath{-}{(T/{T}_{c})}^{2}]}^{\ensuremath{\alpha}}$, where $\ensuremath{\alpha}=1.5$ is the Ginzburg--Landau exponent. We extrapolated ${J}_{c}(0)\ensuremath{\approx}5\ifmmode\times\else\texttimes\fi{}{10}^{7}\text{ }\text{A}/{\text{cm}}^{2}$ for the MoN microfibers and ${J}_{c}(0)\ensuremath{\approx}2.5\ifmmode\times\else\texttimes\fi{}{10}^{5}\text{ }\text{A}/{\text{cm}}^{2}$ for the ${\text{Mo}}_{3}{\text{Sb}}_{7}$ fibers.