Dilute ferromagnetic semiconductors: Physics and spintronic structures

Materials that simultaneously incorporate the properties of ferromagnets and semiconductors, thereby manifesting both spin and electronic degrees of freedom, not only manifest novel physics but also are critical drivers for the emerging field of spintronics. This review focuses on Mn-containing semiconductors, primarily (Ga,Mn)As, and presents an overview of experimental and theoretical advances. Furthermore, the unabated search for new ferromagnetic semiconductors discussed serves as a paradigm for unanticipated discoveries in related materials families embracing superconductors, topological insulators, and organics. This review compiles results of experimental and theoretical studies on thin films and quantum structures of semiconductors with randomly distributed Mn ions, which exhibit spintronic functionalities associated with collective ferromagnetic spin ordering. Properties of p-type Mn-containing III-V as well as II-VI, IV-VI, V sub(2)-VI sub(3), I-II-V, and elemental group IV semiconductors are described, paying particular attention to the most thoroughly investigated system (Ga,Mn)As that supports the hole-mediated ferromagnetic order up to 190 K for the net concentration of Mn spins below 10%. Multilayer structures showing efficient spin injection and spin-related magnetotransport properties as well as enabling magnetization manipulation by strain, light, electric fields, and spin currents are presented together with their impact on metal spintronics. The challenging interplay between magnetic and electronic properties in topologically trivial and nontrivial systems is described, emphasizing the entangled roles of disorder and correlation at the carrier localization boundary. Finally, the case of dilute magnetic insulators is considered, such as (Ga,Mn)N, where low-temperature spin ordering is driven by short-ranged superexchange that is ferromagnetic for certain charge states of magnetic impurities.