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.