A comparison between B- and n-irradiation on MgB2 bulk samples

A comparison of irradiation effects between neutron and high-energy boron-ion irradiation on MgB2 bulk samples is presented. The transition temperature Tc for the neutron irradiation decreases significantly, although the amount of defects is almost the same, of the order (10−2 dpa), for both two cases. This is because the differences of the defect formation process. For the neutron case, mostly damages are originated from nucleus reaction 10B(n, α)7Li. As the result of this, boron sites in the crystal structure are affected seriously. This suggests that the B-originated Fermi surfaces are important for the appearance of the superconductivity in MgB2.