Credit: © 2006 APS

To make spintronic devices, the electrical and optical properties of nanometre-sized semiconducting–magnetic hybrid structures must be controlled and understood on the atomic scale. In manganese-doped semiconductors, these properties have been investigated based on the manipulation of large numbers of Mn atoms. The physical properties and potential applications of magnetic semiconductor structures with only a single Mn atom still require experimental verification.

Now, Yoan Leger and colleagues1 from Université Joseph Fourier-Grenoble, France, and Universitad de Alicante, Spain, have used a combination of an applied voltage and light to control the charge state of CdTe/ZnTe quantum dots (QDs), each doped with a single Mn atom. Importantly, they find that the Mn spin state depends on the charge state of the QDs. Low-temperature photoluminescence measurements at 5 K showed that the QDs can be tuned to one of three different charge states, each with differing spin characteristics.

This study demonstrates how the magnetic properties of Mn-doped semiconductors can be controlled electrically. Furthermore, Leger and co-workers suggest that the way the embedded manganese atoms respond to the charge state of the QDs may be useful for making devices in which digital information can be stored on individual atoms.