T_cand J_cdistribution in in situ processed MgB₂bulk superconductors with/without C doping

Abstract

Temperature dependence of magnetic moment (m−T) and the magnetization (M− ) at 5 K and 20 K of the in situ processed MgB 2 bulk pellets with/without carbon (C) doping were examined. The superconducting critical temperature (T c ), the superconducting transition width (∆T) and the critical current density (J c ) were estimated for ten test samples taken from the MgB 2 bulk pellets. The reliable m−T characteristics associated with the uniform MgB 2 formation were obtained for both MgB 2 pellets. The T c s and ∆Ts of all test samples of the undoped MgB 2 were the same each other as 37.5 K and 1.5 K, respectively. The T c s and ∆Ts of the C-doped MgB 2 were 36.5 K and 2.5 K, respectively. Unlike the m−T characteristics, there existed the difference among the M−H curves of the test samples, which might be caused by the microstructure variation. In spite of the slight T c decrease, the C doping was effective in enhancing the J c at 5 K.

Effects of α-particle beam irradiation on superconducting properties of thin film MgB2superconductors

“…Understanding the vortex pinning mechanism is crucial for that purpose. Further, a multitude of approaches have been developed to enhance the critical current density J c of superconductors: doping [7][8][9], adding nanoparticles [10,11] or a buffer layer [12], irradiation of particle beams [13,14], reduction of grain size [15,16].…”