ABSTRACT
The present chapter reviews the electronic structure and transport properties of quantum dots made of diluted magnetic semiconductors (DMS) made of zincblende II-VI and III-V compounds, such as CdTe and GaAs, where a minor fraction of the cation atoms are replaced by magnetic 3d transition metal atoms, most often Mn. The resulting DMS compounds are denoted by (Cd,Mn)Te, (Ga,Mn)As, etc. We study how transport electrons and the local spins provided by the transition metal atoms affect each other. As in the case of bulk, electrons and holes exert a very different influence on the local spins because of the very different strength of both spin orbit and carrier-local spin coupling of conduction electrons and valence band holes. A distinctive feature of DMS quantum dots is the fact that the controlled addition of a single carrier can result in a dramatic change in their conductivity and magnetization. This result is derived using both an analytical argument where local spins are treated classically and exact diagonalization of the full quantum Hamiltonian in dots with a few Mn atoms, the magnetic dopant that has been most widely studied in this context. Special attention is devoted to the experimentally relevant case of dots doped with an individual Mn atom, an outstanding example of the so‑called single dopant devices [1]. We show how the spin of a single Mn can be controlled by changing the number of carriers in the dot. In this limit, we find a rich interplay between Coulomb Blockade, single spin magnetic anisotropy and transport. In particular, we discuss a strong anisotropic magnetoresistance (AMR) effect in quantum dots with 1 Mn atom gated with 1 heavy hole. Some background material for this chapter is discussed in Chapters 9 and 10, Volume 2, on magnetism in III‑V semiconductors and dilute oxides. Chapter 13, Volume 2, in this book explains how ideas about electrical control of magnetism in semiconductors can be extended to other material systems.201
