The effect of magnesium vacancies on the π intraband scattering in MgxB2 as determined by point contact Andreev reflection

In order to introduce structural defects into the pi band with minimal distortions in the sigma band, bulk samples of varying magnesium content were prepared. Point contact Andreev reflection measurements reveal that the density of states of the pi band and the behavior of the energy gaps in field imply a relative increase of pi band to sigma band scattering with increasing magnesium deficiency. The results are consistent with the observed increase of the low temperature H-c2 value in magnesium deficient MgB2. (c) 2007 American Institute of Physics.