Magnetic properties of neutron irradiated and doped MgB2 superconductors

Studies on the effect of neutron irradiation on MgB₂ superconductor showed a systematic lowering of T_c with increasing neutron fluence. The lower T_c made it difficult to observe the marginal enhancement of flux pinning properties in the neutron irradiated MgB₂ powders. Partial substitution of Mg in MgB₂ by Ti, V and Nb yielded pure samples up to 10 at.% doping level. These substitutions had no affect on T_c, which remained constant at 39 K. The effect of doping Mg by Ti, V, and Nb on the flux pinning properties of MgB₂ was investigated by magnetization measurements. Comparison of the magnetization hysteresis loop widths of the undoped and doped samples showed that the V-doped powders had larger hysteresis loop widths compared to undoped samples indicating enhanced flux pinning in the V-doped samples compared to the undoped and Ti- and Nb-doped samples.