More people, more cities; the energy demand increases in consequence and much of that will rely on next-generation smart materials. Zn-ferrites (ZnFe₂O₄) are nonconventional ceramic materials on account of their unique properties, such as chemical and thermal stability and the reduced toxicity of Zn over other metals. Furthermore, the remarkable cation inversion behavior in nanostructured ZnFe₂O₄ extensively cast-off in the high-density magnetic data storage, 5G mobile communication, energy storage devices like Li-ion batteries, supercapacitors, and water splitting for hydrogen production, among others. Here, we review how aforesaid properties can be easily tuned in various ZnFe₂O₄ nanostructures depending on the choice, amount, and oxidation state of metal ions, the specific features of cation arrangement in the crystal lattice and the processing route used for the fabrication.

The manipulation of the spin degrees of freedom in a solid has been of fundamental and technological interest recently for developing high-speed, low-power computational devices. There has been much work focused on developing highly spin-polarized materials and understanding their behavior when incorporated into so-called spintronic devices. These devices usually require spin splitting with magnetic fields. However, there is another promising strategy to achieve spin splitting using spatial symmetry breaking without the use of a magnetic field, known as Rashba-type splitting. Here we report evidence for a giant Rashba-type splitting at the interface of LaTiO₃ and SrTiO₃. Analysis of the magnetotransport reveals anisotropic magnetoresistance, weak anti-localization and quantum oscillation behavior consistent with a large Rashba-type splitting. It is surprising to find a large Rashba-type splitting in 3d transition metal oxide-based systems such as the LaTiO₃/SrTiO₃ interface, but it is promising for the development of a new kind of oxide-based spintronics.

We performed first-principles calculations of the spin-orbit effect appearing in the electronic structure of the well-known ferroelectric perovskite oxide ${\mathrm{PbTiO}}_3$ and analyzed the results within group-theory-derived models. We evidenced some non-negligible linear Rasbha spin splittings of the unoccupied $p$ bands of Pb atoms and occupied $p$ bands of oxygen atoms. Our calculations also show that a cubic spin splitting is present for the unoccupied $d_{xy}$ bands of Ti atoms. All these spin-orbit effects lead to complex spin textures reversible by switching the electric polarization, which could be used for future spinorbitronic applications. Our results also demonstrate how applying epitaxial strain could be envisaged to tune these properties by changing the relative energy of some of the bands or the magnitude of the linear/cubic coefficients describing the spin splitting.

Based on first-principles methods, we demonstrate that it would be possible to design efficient all-full-Heusler-alloy-based spintronic devices associating ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Si}$ electrodes and nonmagnetic full-Heusler-alloy spacers selected to preserve the half-metallicity of ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Si}$ up to the interface atomic layers. We focus on the ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Si}/{\mathrm{Fe}}_2\mathrm{Ti}\mathrm{Si}$ magnetic tunnel junction, compare the stability range of its different interface terminations, and show that the half-metallicity of the ${\mathrm{Fe}}_2$/$\mathrm{Mn}\mathrm{Si}$-terminated interface even withstands atomic intermixing. The robustness of the half-metallicity of this interface termination is also confirmed in ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Si}/{\mathrm{Fe}}_2\mathrm{V}\mathrm{Al}$ spin valves. With such interfaces, spintronic devices could possess very high magnetoresistive properties.

${\mathrm{CoFe}}_2{\mathrm{O}}_4$ and ${\mathrm{NiFe}}_2{\mathrm{O}}_4$ are well-known insulating and ferrimagnetic spinel ferrites with high Curie temperatures, an important characteristic for electronic and spintronic applications. We used first-principles calculations to investigate how their electronic and magnetic properties can be altered or tuned by the presence of structural point defects. We considered successively the effects of cation distribution in the spinel lattice for stoichiometric compounds and of atom substitutions or vacancies. Our calculations demonstrate that a deviation from the perfectly inverse distribution of cations increases the magnetization and decreases the width of the band gap at the Fermi level. In contrast to cation vacancies, oxygen vacancies are not expected to strongly affect the magnetization. We show that ${\mathrm{NiFe}}_2{\mathrm{O}}_4$ crystals with an excess of Ni cations can display a spin-polarized hole conductivity. We finally calculated the formation energy of the different defects and we give details on their gap states.

We used the DFT + U method to describe the modification of the physical properties induced by cationic point defects in cubic magnetite Fe3O4. We considered the case of Fe vacancies and interstitial atoms in non-stoichiometric magnetite, and of Frenkel defects in a stoichiometric crystal. For each of these defects, we give results on the modification of the magnetic moment of atoms near the defect. We describe the local reorganization of the electric charge which is responsible for changes in the average oxidation degree of Fe atoms. We show that gap states, when they exist, do not destroy the half-metallic character of magnetite. Fe defects, however, change the filling of bands crossing the Fermi level and must be mostly responsible for a decrease in the magnetization.