Evaluation of Drought Tolerance in Arkansas Cowpea Lines at Seedling Stage

Cowpea [Vigna unguiculate (L.) Walp.] is not only a healthy, nutritious and versatile leguminous crop, it also has a relatively high adaptation to drought. Researches have shown that cowpea lines have a high tolerance to drought, and many of them can survive over 40 days under very hot and dry conditions. The cowpea (Southern pea) breeding program at the University of Arkansas (UA) has been active for over 50 years and has produced more than 1,000 advanced breeding lines. And the purpose of this study is to evaluate the drought-tolerant ability in Arkansas cowpea lines and use the drought tolerant lines in cowpea production or as parents in cowpea breeding. A total of 36 UA breeding lines were used to screen drought tolerance at the seedling stage in this study. The experiment was conducted in greenhouse using completely randomized design (CRD) with two replicates. Drought stress was applied for four weeks, and three drought tolerant related traits were collected and analyzed. Results showed that cowpea breading line: 17-81, 17-86, Early Scarlet, and AR Blackeye #1 were found to be drought tolerant

Ferroelectricity controlled chiral spin textures and anomalous valley Hall effect in the Janus magnet-based multiferroic heterostructure

Realizing effective manipulation and explicit identification of topological spin textures are two crucial ingredients to make them as information carrier in spintronic devices with high storage density, high data handling speed and low energy consumption. Electric-field manipulation of magnetism has been achieved as a dissipationless method compared with traditional regulations. However, the magnetization is normally insensitive to the electric field since it does not break time-reversal symmetry directly, and distribution of topological magnetic quasiparticles is difficult to maintain due to the drift arising from external fluctuation, which could result in ambiguous recognition between quasiparticles and uniform magnetic background. Here, we demonstrate that electric polarization-driven skyrmionic and uniform ferromagnetic states can be easily and explicitly distinguished by transverse voltage arising from anomalous valley Hall effect in the Janus magnet-based multiferroic heterostructure LaClBr/In2Se3. Our work provides an alternative approach for data encoding, in which data are encoded by combing topological spin textures with detectable electronic transport.Comment: published in 2D materials, 9, 045030 (2022

Dzyaloshinskii-Moriya interaction and magnetic skyrmions induced by curvature

Realizing sizeable Dzyaloshinskii-Moriya interaction (DMI) in intrinsic two-dimensional (2D) magnets without any manipulation will greatly enrich potential application of spintronics devices. The simplest and most desirable situation should be 2D magnets with intrinsic DMI and intrinsic chiral spin textures. Here, we propose to realize DMI by designing periodic ripple structures with different curvatures in low-dimensional magnets and demonstrate the concept in both one-dimensional (1D) CrBr2 and two-dimensional (2D) MnSe2 magnets by using first-principles calculations. We find that DMIs in curved CrBr2 and MnSe2 can be efficiently controlled by varying the size of curvature c, where c is defined as the ratio between the height h and the length l of curved structure. Moreover, we unveil that the dependence of first-principles calculated DMI on size of curvature c can be well described by the three-site Fert-L\'evy model. At last, we uncover that field-free magnetic skyrmions can be realized in curved MnSe2 by using atomistic spin model simulations based on first-principles calculated magnetic parameters. The work will open a new avenue for inducing DMI and chiral spin textures in simple 2D magnets via curvature.Comment: Published on Physical Review B 106, 05442

Large and tunable magnetoresistance in van der Waals ferromagnet/semiconductor junctions

Magnetic tunnel junctions (MTJs) with conventional bulk ferromagnets separated by a nonmagnetic insulating layer are key building blocks in spintronics for magnetic sensors and memory. A radically different approach of using atomically-thin van der Waals (vdW) materials in MTJs is expected to boost their figure of merit, the tunneling magnetoresistance (TMR), while relaxing the lattice-matching requirements from the epitaxial growth and supporting high-quality integration of dissimilar materials with atomically-sharp interfaces. We report TMR up to 192% at 10 K in all-vdW Fe3GeTe2/GaSe/Fe3GeTe2 MTJs. Remarkably, instead of the usual insulating spacer, this large TMR is realized with a vdW semiconductor GaSe. Integration of semiconductors into the MTJs offers energy-band-tunability, bias dependence, magnetic proximity effects, and spin-dependent optical-selection rules. We demonstrate that not only the magnitude of the TMR is tuned by the semiconductor thickness but also the TMR sign can be reversed by varying the bias voltages, enabling modulation of highly spin-polarized carriers in vdW semiconductors

Large and tunable magnetoresistance in van der Waals Ferromagnet/Semiconductor junctions

Magnetic tunnel junctions (MTJs) with conventional bulk ferromagnets separated by a nonmagnetic insulating layer are key building blocks in spintronics for magnetic sensors and memory. A radically different approach of using atomically-thin van der Waals (vdW) materials in MTJs is expected to boost their figure of merit, the tunneling magnetoresistance (TMR), while relaxing the lattice-matching requirements from the epitaxial growth and supporting high-quality integration of dissimilar materials with atomically-sharp interfaces. We report TMR up to 192% at 10 K in all-vdW Fe3GeTe2/GaSe/Fe3GeTe2 MTJs. Remarkably, instead of the usual insulating spacer, this large TMR is realized with a vdW semiconductor GaSe. Integration of two-dimensional ferromagnets in semiconductor-based vdW junctions offers gate-tunability, bias dependence, magnetic proximity effects, and spin-dependent optical-selection rules. We demonstrate that not just the magnitude, but also the TMR sign is tuned by the applied bias or the semiconductor thickness, enabling modulation of highly spin-polarized carriers in vdW semiconductors

Strain-tunable ferromagnetism and chiral spin textures in two-dimensional Janus chromium dichalcogenides

Using first-principles calculations and micromagnetic simulations, we systematically investigate the magnetic properties of two-dimensional Janus chromium dichalcogenides (CrXTe, X = S, Se) under strain. We find that the CrSTe monolayer has high Curie temperature (T-c) of 295 K and an out-of-plane magnetic anisotropy. The CrSeTe monolayer has large Dzyaloshinskii-Moriya interaction (DMI) which can host chiral Neel domain wall (DW), and under an external magnetic field, the skyrmion states can be induced. As tensile strain increases, ferromagnetic exchange coupling and perpendicular magnetic anisotropy of Janus CrXTe monolayers both increase significantly, and the magnitude of DMI is reduced, which results in the giant ferromagnetism enhancement. Interestingly, for CrSeTe monolayer, distinct spin textures from chiral DW to uniform ferromagnetic states are induced under tensile strain. Moreover, the diameter and density of skyrmions in CrSeTe can be tuned by the amplitude of external magnetic field and strain. These findings highlight that the Janus CrXTe monolayers as good candidates for spintronic nanodevices

Giant enhancement of perpendicular magnetic anisotropy and induced quantum anomalous Hall effect in graphene/NiI2 heterostructures via tuning the van der Waals interlayer distance

Using first-principles calculations, we reveal that the perpendicular magnetic anisotropy of NiI2 monolayer can be effectively enhanced via decreasing the interlayer distance of graphene/NiI2 (Gr/NiI2) van der Waals (vdW) heterostructures. Furthermore, by analyzing the atomic-resolved magnetocrystalline anisotropy energy (MAE), orbital hybridization-resolved MAE and the density of states we elucidate that this magnetic anisotropy enhancement mainly originated from the electronic states change of 5p orbitals of interfacial I atoms. At the same time, we find that the NiI2 substrate induces strong magnetic proximity effects on graphene and the quantum anomalous Hall effect (QAHE) can be acquired by decreasing the interlayer spacing. Our work demonstrates the control of magnetic anisotropy of two-dimensional ferromagnetic materials via tuning vdW interlayer distance, and provides a van der Waals system to realize the QAHE

Reversible control of Dzyaloshinskii-Moriya interaction at the graphene/Co interface via hydrogen absorption

Using first-principles calculations, we investigate the impact of hydrogenation on the Dzyaloshinskii-Moriya interaction (DMI) at graphene/Co interface. We find that both the magnitude and chirality of DMI can be controlled via hydrogenation absorbed on graphene surface. Our analysis using density of states combined with first-order perturbation theory reveals that the spin splitting and the occupation of Co-d orbitals, especially the d(xz) and d(z2) states, play a crucial role in defining the magnitude and the chirality of DMI. Moreover, we find that the DMI oscillates with a period of two atomic layers as a function of Co thickness what could be explained by analysis of out-of-plane of Co orbitals. Our work elucidates the underlying mechanisms of interfacial DMI origin and provides an alternative route of its control for spintronic applications