Publication Details

Ghorbani, SR, Wang, P, Hossain, M, Yao, Q, Dou, SX, Lee, S, Chung, KC & Kim, YK (2010), Strong competition between the delta l and delta T-c flux pinning mechanisms in MgB2 doped with carbon containing compounds, Journal of Applied Physics, 107(11), pp. 1-4.


The transport and magnetic properties of 10 wt % malic acid and 5 wt % nanocarbon doped MgB2 have been studied by measuring the resistivity (p), critical current density (jc), connectivity factor (AF), irreversibility field (Hirr), and upper critical field (Hc2). The pinning mechanisms are studied in terms of the collective pinning model. It was found that both mean free path (δl) and critical temperature (δTc) pinning mechanisms coexist in both doped MgB2. For both the malic acid and nanocarbon doped samples, the temperature dependence of the crossover field, which separates the single vortex and the small bundle pinning regime, Bsb(T), shows that the δl pinning mechanism is dominant for temperatures up to t(T/Tc)=0.7 but the δTc pinning mechanism is dominant for t >0.7. This tendency of coexistence of the δl and the δTc pinning mechanism is in strong contrast with the pure MgB2, in which the δTc pinning mechanism is dominant over a wide temperature range below Tc. It was also observed that the connectivity factor, active cross-sectional area fraction (AF), are 0.11 and 0.14 for the nanocarbon and the malic acid doped MgB2, respectively, indicating that there are still rooms for further improving jc performance.

Grant Number

ARC/DP0770205, ARC/LX0882225