Mechanical and electronic properties of ferromagneticGa1−xMnxAsusing ultrafast coherent acoustic phonons

Abstract

Ultrafast two-color pump-probe measurements, involving coherent acoustic phonon waves, have provided information simultaneously on the mechanical properties and on the electronic structure of ferromagnetic ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$. The elastic constants ${C}_{11}$ of ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$ $(0.03\ensuremath{\le}x\ensuremath{\le}0.07)$ are observed to be systematically smaller than those of GaAs. Both ${C}_{11}$ and ${V}_{\text{s}}$ measured in ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$ are found to increase with temperature $(78\text{ }\text{K}\ensuremath{\le}T\ensuremath{\le}295\text{ }\text{K})$, again in contrast to the opposite behavior in GaAs. In addition, our experimental results indicate a small blueshifting of the fundamental band gap of ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$ as Mn concentration increases.