Gating in ferromagnetic semiconductor*

Ferromagnetic semiconductors have the potential of revolutionizing the way current electronic devices work: more so, because they are compatible with current fabrication lines and can easily be integrated with today technology. Particular interest lies in III-V Diluted Magnetic Semiconductor (DMS), where the ferromagnetism is hole-mediated and the Curie temperature can therefore be tuned by changing the concentration of free carriers\footnote{T. Dietl \textit{et al.}, Phys. Rev. B \textbf{63}, 195205 (2001)}. In these systems, most of the effort is currently applied toward the fabrication of devices working at room-temperature: this implies high carrier density accompanied by low mobility and short mean free path. We will report our results in exploring devices with low hole concentration and Curie temperature ($\sim$ 4 K) and we will discuss the effect of local gating\footnote{H. Ohno \textit{et al.}, Nature \textbf{408}, 944 (2000)} in light of possible applications to the fabrication of ferromagnetic quantum dots.