Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTunable Magnetism and Insulator-Metal Transition in Bilayer Perovskites
114
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Two-dimensional (2D) transition-metal oxide perovskites greatly expand the field of available 2D multifunctional material systems. Here, based on density functional theory calculations, we predicted the presence of ferromagnetism orders accompanying with an insulator-metal phase transition in bilayer $KNbO_{3}$ and $KTaO_{3}$ by applying strain engineering and/or external electric field. Our results will contribute to the applications of few-layer transition metal oxide perovskites in the emerging spintronics and straintronics.
rate research
Read More
Diverse interlayer tunability of physical properties of two-dimensional layers mostly lies in the covalent-like quasi-bonding that is significant in electronic structures but rather weak for energetics. Such characteristics result in various stacking orders that are energetically comparable but may significantly differ in terms of electronic structures, e.g. magnetism. Inspired by several recent experiments showing interlayer anti-ferromagnetically coupled CrI3 bilayers, we carried out first-principles calculations for CrI3 bilayers. We found that the anti-ferromagnetic coupling results from a new stacking order with the C2/m space group symmetry, rather than the graphene-like one with R3 as previously believed. Moreover, we demonstrated that the intra- and inter-layer couplings in CrI3 bilayer are governed by two different mechanisms, namely ferromagnetic super-exchange and direct-exchange interactions, which are largely decoupled because of their significant difference in strength at the strong- and weak-interaction limits. This allows the much weaker interlayer magnetic coupling to be more feasibly tuned by stacking orders solely. Given the fact that interlayer magnetic properties can be altered by changing crystal structure with different stacking orders, our work opens a new paradigm for tuning interlayer magnetic properties with the freedom of stacking order in two dimensional layered materials.
We construct an effective Hamiltonian for the motion of electrons among the transition metal ions of ordered double perovskites like Sr2FeMoO6. in which strong intra-atomic Coulomb repulsion U is present in only one of the inequivalent transition metal sites. Using a slave-boson formalism, we construct a phase diagram which describes a charge transfer transition between insulating and metallic behavior as the parameters of the model are changed. The parameters for Sr2FeMoO6 are estimated from first-principles calculations and a transition to the insulating state with negative pressure is obtained.
Using first-principles calculations, we investigate six transition-metal nitride halides (TMNHs): HfNBr, HfNCl, TiNBr, TiNCl, ZrNBr, and ZrNCl as potential van der Waals (vdW) dielectrics for transition metal dichalcogenide (TMD) channel transistors. We calculate the exfoliation energies and bulk phonon energies and find that the six TMNHs are exfoliable and thermodynamically stable. We calculate both the optical and static dielectric constants in the in-plane and out-of-plane directions for both monolayer and bulk TMNHs. In monolayers, the out-of-plane static dielectric constant ranges from 5.04 (ZrNCl) to 6.03 (ZrNBr) whereas in-plane dielectric constants range from 13.18 (HfNBr) to 74.52 (TiNCl). We show that the bandgap of TMNHs ranges from 1.53 eV (TiNBr) to 3.36 eV (HfNCl) whereas the affinity ranges from 4.01 eV (HfNBr) to 5.60 eV (TiNCl). Finally, we estimate the dielectric leakage current density of transistors with six TMNH monolayer dielectrics with five monolayer channel TMDs (MoS2, MoSe2, MoTe2, WS2, and WSe2). For p-MOS TMD channel transistors, 19 out of 30 combinations have a smaller leakage current compared to monolayer hexagonal boron nitride (hBN), a well-known vdW dielectric. The smallest monolayer leakage current of 2.14*10-9 A/cm2 is predicted for a p-MOS WS2 transistor with HfNCl as a gate dielectric. HfNBr, HfNCl, ZrNBr, and ZrNCl are also predicted to yield small leakage currents in certain p-MOS TMD transistors.
We investigate the interactions between two identical magnetic impurities substituted into a graphene superlattice. Using a first-principles approach, we calculate the electronic and magnetic properties for transition-metal substituted graphene systems with varying spatial separation. These calculations are compared for three different magnetic impurities, manganese, chromium, and vanadium. We determine the electronic band structure, density of states, and Millikan populations (magnetic moment) for each atom, as well as calculate the exchange parameter between the two magnetic atoms as a function of spatial separation. We find that the presence of magnetic impurities establishes a distinct magnetic moment in the graphene lattice, where the interactions are highly dependent on the spatial and magnetic characteristic between the magnetic atoms and the carbon atoms, which leads to either ferromagnetic or antiferromagnetic behavior. Furthermore, through an analysis of the calculated exchange energies and partial density of states, it is determined that interactions between the magnetic atoms can be classified as an RKKY interaction.
The spin Hall effect (SHE) is highly promising for spintronic applications, and the design of materials with large SHE can enable ultra-low power memory technology. Recently, 5d-transition metal oxides have been shown to demonstrate a large SHE. Here we report large values of SHE in four 5d-transition metal anti-perovskites which makes these anti-perovskites promising spintronic materials. We demonstrate that these effects originate in the mixing of dx2-y2 and dxy orbitals caused by spin orbit coupling.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
