Concurrent doping effect of Ti and nano-diamond on flux pinning of MgB2

Abstract Nano-diamond and titanium concurrently doped MgB 2 nanocomposites have been prepared by solid state reaction method. The effects of carbon and Ti concurrent doping on J c – H behavior and pinning force scaling features of MgB 2 have been investigated. Although T c was slightly depressed, J c of MgB 2 have been significantly improved by the nano-diamond doping, especially in the high field region. In the mean time, the J c value in low field region is sustained though concurrent Ti doping. Microstructure analysis reveals that when nano-diamond was concurrently doped with titanium in MgB 2 , a unique nanocomposite in which TiB 2 forms a thin layer surrounding MgB 2 grains whereas nano-diamond particles were wrapped inside the MgB 2 grains. Besides, nano-diamond doping results in a high density stress field in the MgB 2 samples, which may take responsibility for the Δ κ pinning behavior in the carbon-doped MgB 2 system.