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The spin degeneracy in antiferromagnets hinders the spin splitting valleys, which limits their application in spintronic and valleytronic devices. In the two dimensional (2D) antiferromagnetic (AFM) heterostructure MnPSe3/WSe2, the coexistence of spin–orbit, spin–valley, and interlayer coupling produces the spin splitting valence band maximum (VBM) from the nonmagnetic semiconductor WSe2 and the spin splitting conduction band minimum (CBM) from the antiferromagnet MnPSe3, which results in a sizable spin- and k-resolved valley splitting larger than 30 meV. In addition, normal strain proves to be an effective approach to regulate valley splitting through interlayer coupling.

Two-dimensional (2D) heterostructures can generate new properties that are not possessed in their constituents. Monolayer transition metal dichalcogenides (TMDs) MX2 (M = Mo, W; X = Se, Te) are an ideal system to produce the valley degree of freedom, furthermore, the magnetic proximity effect in MX2/Cr2Ge2Te6 heterostructures can lift the valley degeneracy and produce nonvolatile valley polarization (VP). Taking the WSe2/Cr2Ge2Te6 heterostructure as an example, we demonstrate that the normal strain can modify the magnetic proximity effect and tune the VP. In addition, comparing the different MX2/Cr2Ge2Te6 heterostructures, we find that the VP not only relies on the transition metal atom M, but also depends on the super–super exchange “–X–Te–” which connects the M atom and the magnetic Cr atom. The induced VP in MX2 follows the sequence: WTe2 > WSe2 > MoTe2 > MoSe2. Our investigation reveals the tunability of VP in MX2/Cr2Ge2Te6 heterostructures, which will be of great significance in valleytronics.

The ferromagnetism of the two dimensional (2D) Cr2Ge2Te6 atomic layers with the perpendicular magnetic anisotropy and the Curie temperature 30-50 K has recently been experimentally confirmed. By performing the density-functional theory calculations, we demonstrate that the magnetic properties of bilayer Cr2Ge2Te6 can be flexibly tailored, due to the effective band structure tuning by the external electric field. The electric field induces the semiconductor-metal transition and redistributes charge and spin between the two layers. Furthermore, the magnetic anisotropy energy of the bilayer Cr2Ge2Te6 can be obviously enhanced by the electric field, which is helpful to stabilize the long-range ferromagnetic order. Our study about the electric manipulation of magnetism based on the band structure engineering generally exists in 2D magnetic systems and will be of great significance in low-dimensional all-electric spintronics.

Engineering the electronic band structure of material systems enables the unprecedented exploration of new physical properties that are absent in natural or as-synthetic materials. Half metallicity, an intriguing physical property arising from the metallic nature of electrons with singular spin polarization and insulating for oppositely polarized electrons, holds a great potential for a 100% spin-polarized current for high-efficiency spintronics. Conventionally synthesized thin films hardly sustain half metallicity inherited from their 3D counterparts. A fundamental challenge, in systems of reduced dimensions, is the almost inevitable spin-mixed edge or surface states in proximity to the Fermi level. Here, we predict electric field-induced half metallicity in bilayer A-type antiferromagnetic van der Waals crystals (i.e., intralayer ferromagnetism and interlayer antiferromagnetism), by employing density functional theory calculations on vanadium diselenide. Electric fields lift energy levels of the constituent layers in opposite directions, leading to the gradual closure of the gap of singular spin-polarized states and the opening of the gap of the others. We show that a vertical electrical field is a generic and effective way to achieve half metallicity in A-type antiferromagnetic bilayers and realize the spin field effect transistor. The electric field-induced half metallicity represents an appealing route to realize 2D half metals and opens opportunities for nanoscale highly efficient antiferromagnetic spintronics for information processing and storage.

Lithium-ion batteries have been widely used in daily electric appliance, but abusive accidents occurred from time to time. Lithium-ion batteries composed of various electrolytes (containing organic solvents, inorganic salts), binder, and electrode materials, which may be unstable under some abnormal conditions. The formulation or components of electrolytes played a crucial factor in affecting reactive hazards within the cell. In order to meet safety requirements of the lithium-ion batteries on electronic device, reseachers and scholars are continuing to do further studies on the important issues in relation to the lithium-ion batteries. This study aims to apply the differential scanning calorimeter for measuring the thermal or reactive hazards of the organic solvents related to the formulation of the electrolytes. Besides, thermal instabilities of lithiated graphite or deposited lithium with electrolytes were simulated by the reactions between metallic lithium (Li) and organic carbonates of linear and cyclic structures. Exothermic onset temperatures and enthalpy changes were measured and analyzed. Results showed that the thermal behaviors of these organic carbonates themselves or with lithium hexafluorophosphate liberated less enthalpy changes. However, violent exothermic reactions were detected between the linear or cyclic carbonates and lithium metal with larger enthalpy change larger than 1,000 J g−1 of lithium. This can be observed by Li reacted with diethyl carbonate at surprisingly lower onset temperature about 46.6 °C.

Interface effects in magnetic nanostructures play a critical role in the magnetic properties. By using first-principles density functional theory calculations, we investigate the electronic and magnetic properties of Fe/SrTiO3 interfaces, in which both the nonpolar surface SrTiO3(0 0 1) and the polar surface SrTiO3(1 1 0) are considered. A particular emphasis is placed on the magnetic anisotropy energy (MAE). Comparing MAE of the Fe/SrTiO3 interfaces and the corresponding Fe monolayers, we find the Fe/SrTiO3(0 0 1) interface decreases MAE, while the Fe/SrTiO3(1 1 0) interface increases MAE. The interface orbital hybridization and orbital magnetic moments are analyzed in detail to understand the different interface magnetic anisotropy. Our investigation indicates that interface engineering can be an effective way to modulate the magnetic properties.