The ferromagnetic properties of Ge magnetic quantum dots doped with Mn

We present a synthesis of Ge:Mn magnetic quantum dots (QDs) and an evaluation of their ferromagnetic properties. The QDs were grown from a GeH4/Ar mixed gas under constant flow conditions at 400 °C by means of a plasma-enhanced chemical vapor deposition (PECVD) process, then doped with Mn by a magnetic sputtering technique and annealed at 600 °C. The QDs, with a composition of Ge0.88Mn0.12 according to their energy spectrum, showed widely opened hysteresis loops, with large remnant magnetizations Mr of 0.14 × 10−4 and 0.25 × 10−4 emu/g for the as-grown and annealed samples, respectively. Moreover, the average value of the moment per Mn atom was found to be as high as 2.36 μB at room temperature, showing that the Ge1−xMnx QDs constitute an intrinsic diluted magnetic semiconductor. The unprecedented colossal moment is attributed to an effective RKKY exchange coupling interaction between the Mn ions mediated by holes.