de Haas-van Alphen effect investigation of the electronic structure of Al substituted MgB_2

Abstract

We report a de Haas-van Alphen (dHvA) study of the electronic structure of Al doped crystals of MgB${}_2$. We have measured crystals with $\sim 7.5$% Al which have a $T_c$ of 33.6 K, ($\sim 14$% lower than pure MgB${}_2$). dHvA frequencies for the $\ddot{I}ƒ$ tube orbits in the doped samples are lower than in pure MgB${}_2$, implying a $16\pm 2$ reduction in the number of holes in this sheet of Fermi surface. The mass of the quasiparticles on the larger $\ddot{I}ƒ$ orbit is lighter than the pure case indicating a reduction in electron-phonon coupling constant $\hat{I}»$. These observations are compared with band structure calculations, and found to be in excellent agreement.

4 pages with figures