An n-type tunable two-dimensional ferromagnetic semiconductor

In the past two decades ferromagnetic semiconductors have been the focus of intense studies because of their potential technological application for spintronics. Particular attention has been dedicated to III-V Diluted Magnetic Semiconductors (DMS), where the ferromagnetism (FM) 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 structures, the Anomalous Hall Effect (AHE) has played a key role in establishing that FM is hole-mediated. We will present data that show the first evidence of electron-mediated FM in GaMnAs. Our heterostructure has a low carrier density ($\sim$ $1.1E12 cm^-2$), a mobility of $\sim$ $600 cm^2/(Vs)$ and excellent gating capabilities. We will also present data that show the first clear bound on the AHE in an electron-mediated DMS and find it much reduced in magnitude when compared to the case of hole-mediated FM.