# Unexpected Ferromagnetism--A Review
## 4 Applications and Future Trends  
One of the potential applications for diluted magnetic oxides (and possibly other materials having \"diluted\" magnetic properties) is the obtaining of performant materials that simultaneously possess electric and magnetic properties, eventually combined with transparency for use in electronics. The other major target for these materials is their promising application in spintronics due to their expected controlled spin-polarization carriers injection [116]. The spintronics (abbreviation for spin-transport electronics) domain is based on the study of the electron spin and their associated magnetic moment for the applications in efficient solid-state devices, such as those for data storage and information transfer, as briefly reviewed in [117]. In the same review [117], the authors believe that an \"ultimate goal for spintronics\" in the longer term is to replace the CMOS (complementary metal-oxide-semiconductor) transistor with an equivalent device using extremely low power. From the spintronic point of view, their electrical charge and the spin of electrons are controlled to operate the information circuits [116]. Consequently, this kind of manipulation of spins (from electrons or holes) in semiconductors has immense potential from high-speed information processing, accompanied by their storage in non-volatile memory using low power, and can open a path for quantum computing [116; 118]. Other spintronic devices based on magnetic semiconductors are spin-field emission transistors (spin-FETs) and spin logic gates [119]. The authors from [116] enumerate some of the technical problems that need to be resolved in order for the spintronics to be industrially feasible: \"efficient injection, transport, control and manipulation, and detection of spin polarization and spin-polarized currents\". [PERSON] et al. [120] carefully revised the vast domain of zinc oxide films doped with transitional ions (such as monodopants Co, Mn, Sc, Ti, V, Cr, Fe, Ni, Cu, and also with FeCu, CoCu, CoFe, CoAl, MnCo, MnSn, MnAl, MnN, MnP, MnP, MnCu, CuGa, CoLi, CoN, CuN, as pairs of co-dopants) for possible applications in spintronics, highlighting that there still remains a lot of questions about its origin as well as the use for spintronics [120]. In turn, the authors concluded that the origin of room temperature ferromagnetism in these systems was unambiguously proved to be the structural defects, pointing out that the carriers responsible for carrier-mediated exchange were only \"natural byproducts\" of the defect creation in these zinc oxide-based materials [120]. Moreover, they claim that spintronic devices of second-generation, containing these ZnO special films with not only ferromagnetic but also with piezoelectric, ferroelectric, and optical properties, can be fabricated devices that can induce and manipulate spin-polarized electrons (or holes) in a semiconductor [120]. Magnetic tunnel junctions (MTJs) are devices whereby the tunneling of electrons through the dielectric layer is controlled by their spin via the electrodes made from ferromagnetic materials, which can have parallel or antiparallel magnetizations [121]. For example, in [122] a functional MTJ device is described as having one electrode made from a co-doped rutile TiO\({}_{2}\) FM semiconductor, the other being metallic (Fe\({}_{0.1}\)Co\({}_{0.9}\)) separated by an AlOx dielectric barrier. Thus, the Ti\({}_{1-x}\)Co\({}_{x}\)O\({}_{2-\delta}\) film was demonstrated to be able to act as a spin injection electrode in this device, having a TMR ratio of \(\sim\)11% at 15 K [122]. Unfortunately, in this case, the TMR diminished as the temperature increased and disappeared at 180 K due to the low quality of amorphous alumina barrier, which induces inelastic tunneling conduction at higher temperatures [122].