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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Electrochemical Intercalation and Exfoliation of CrSBr into Ferromagnetic Fibers and Nanoribbons

Abstract Recent studies dedicated to layered van der Waals crystals have attracted significant attention to magnetic atomically thin crystals offering unprecedented opportunities for applications in innovative magnetoelectric, magneto‐optic, and spintronic devices. The active search for original platforms for the low‐dimensional magnetism study has emphasized the entirely new magnetic properties of two dimensional (2D) semiconductor CrSBr. Herein, for the first time, the electrochemical exfoliation of bulk CrSBr in a non‐aqueous environment is demonstrated. Notably, crystal cleavage governed by the structural anisotropy occurred along two directions forming atomically thin and few‐layered nanoribbons. The exfoliated material possesses an orthorhombic crystalline structure and strong optical anisotropy, showing the polarization dependencies of Raman signals. The antiferromagnetism exhibited by multilayered CrSBr gives precedence to ferromagnetic ordering in the revealed CrSBr nanostructures. Furthermore, the potential application of CrSBr nanoribbons is pioneered for electrochemical photodetector fabrication and demonstrates its responsivity up to 30 µA cm −2 in the visible spectrum. Moreover, the CrSBr‐based anode for lithium‐ion batteries exhibited high performance and self‐improving abilities. This anticipates that the results will pave the way toward the future study of CrSBr and practical applications in magneto‐ and optoelectronics.

Chemistry↗
DOE OSTI2017

Study of Electronic, Mechanical, Magnetic, and Optical Properties of Mg{sub 0.75}TM{sub 0.25}S/Se (TM = Fe, Co, Ni): A First Principle Approach

A systematic study of the magnetism, mechanical, and optical behaviors of Mg{sub 0.75}TM{sub 0.25}S/Se (TM = Fe, Co, Ni) ordered alloys was conducted using the full-potential linearized augmented plane wave plus local orbital method. The ferromagnetic (FM) and antiferromagnetic (AFM) ground state energy differences and enthalpy of formation scrutinized their dynamical stability in the FM state. The elastic parameters decided their mechanical stability, ductile behavior, and partial ionic and covalent characters. Moreover, the calculated band structures and density of states revealed the type and origin of magnetism in terms of exchange splitting energies and exchange constants. The Fe- and Ni-doped MgS/Se alloys exhibited half metallic ferromagnetic (HMF) characteristics, while the Co-doped MgS/Se alloy depicted ferromagnetic semiconducting characters. A reduction in the magnetic moments of the transition metals was observed compared with their free space value, which is due to strong p-d hybridization. Furthermore, the optical spectrum showed the maximum light absorbed in the visible and in the UV region of the electromagnetic spectrum, which makes them potential candidates for optoelectronic and spintronic device applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

First-Principle Investigation of V and Cr Doping on the Dilute Magnetic Semiconducting Properties of Rutile SnO{sub 2}: a Modified Becke-Johnson (TB-mBJ) Exchange Potential Study

Theoretical investigations on rutile SnO{sub 2} doped with V and Cr were performed by using recently implemented Tran and Blaha’s modified Becke-Johnson exchange potential model (TB-mBJ) based on density functional theory. The electronic, magnetic, dielectric and optical properties of V and Cr-doped tin oxide have been calculated by full-potential linearized augmented plane wave method (FP-LAPW) by WIEN2k code. The present works demonstrate accurate prediction of band structures and properties using the TB-mBJ model. The calculated values of magnetic moment, dielectric constant and refractive index of doped and undoped compounds agree well with the experimental results. The TB-mBJ model is a direct method without using empirical corrections and hence, the furnished data are useful in material modelling for spintronics applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

d{sup 0} Half-Metallic Ferromagnetism in CaN and CaAs Pnictides: an Ab Initio Study

Conventional magnetism occurs in systems which contain transition metals or rare earth ions with partially filled d or f shells. It is theoretically predicted that compounds of groups IA and IIA with IV and V, in some structural phases, are ferromagnetic half-metals which made them new candidates for spintronics applications. Employing density functional theory (DFT), we investigate magnetism in binary compounds CaN and CaAs. Regarding the structure of analogous magnetic materials and experimental results of CaAs synthesis, we have considered two cubic structures: rocksalt (RS) and zincblende (ZB), and four hexagonal structures: NiAs, wurtzite (WZ), anti-NiAs, and NaO. The calculated results show that CaN in cubic, NiAs, and wurtzite structures, and CaAs only in zincblende phase have ferromagnetic ground states with a magnetic moment of 1 μ{sub B}. Electronic structure analysis of these materials indicates that magnetism originates from anion p states. Existence of flat p bands and consequently high density of states at the Fermi level of magnetic structures gives rise to Stoner spin splitting and spontaneous ferromagnetism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

A Model Study of Substrate Effect on the Neutron-Scattering Spectra of Ferromagnetic Ordered Graphene

Graphene as a possible new magnetic material has stimulated research interest for application in spintronic devices. Pristine graphene does not show magnetism due to equivalence of the two sub-lattices of carbon atoms. It is predicted that impurity effects, substrate-induced gap, and defects, are expected to produce in-equivalence in two carbon sub-lattices leading to magnetism. The spins on the same sub-lattices are found to exhibit ferromagnetic order and spins of different sub-lattices are found to exhibit anti-ferromagnetic order. We consider here impurity and substrate effects as the cause of generation of magnetism in graphene. We report here a microscopic tight-binding study of frequency-dependent neutron scattering spectra for ferromagnetic ordering in the graphene systems. The tight-binding Hamiltonian consists of electron hoppings upto third nearest neighbors and substrate and impurity effects in the presence of Coulomb interaction of electrons separately at two in-equivalent A and B sub-lattices of graphene. We calculate the two-particle electron Green’s functions by using Zubarev’s Green’s function technique. The frequency-dependent scattering intensity of the system is computed numerically. The spectra displays a sharp peak at the neutron momentum transfer energy at low energies and another higher-energy peak appearing at substrate-induced gap.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

First-Principle Calculation of Electronic Structures and Magnetic Properties of Heusler Alloys Co{sub 2}ZrPb and Zr{sub 2}MnBa

Using first-principle method of density functional theory (DFT), we have investigated the underlying mechanism related to the electronic and magnetic properties of novel full Heusler alloys Co{sub 2}ZrPb and Zr{sub 2}MnB. Our results show that compound Zr{sub 2}MnB is a nonmagnetic semiconductor whereas Co{sub 2}ZrPb is half metallic a magnetic moment of 2 μ{sub B} per formula unit. It exhibits a large spin gap of 0.334 eV for equilibrium lattice constant and has excellent half-metallic ferrimagnetism with 100% spin polarization at the Fermi level. The half-metallicity of Co{sub 2}ZrPb is stable against lattice change of −2.6 to 0.83%. The Co-based Heusler alloys are expected to be ideal candidates for spintronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Hydrogen Annealing Effect on the Magnetic Properties of ZnCoO/MoS{sub 2} Hybrid

The ZnCoO/MoS{sub 2} hybrid is successfully synthesized through a general and facile process. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectra reveal that the hybrid consists of wurtzite ZnCoO and few layers of MoS{sub 2}, which shows a paramagnetic property. In contrast, the hybrid presents clear magnetic hysteresis at room temperature with a H{sub 2} post-annealing process. No Co metal nanoclusters can be identified by XRD and HRTEM. The red shift of E{sub 2g}{sup 1} and A{sub 1g} peak indicates the strain effect induced by H{sub 2} annealing. On the other hand, the disappeared peak at 477 cm{sup −1} can be ascribed to the modification of the interface and surface state of the ZnCoO. Temperature-dependent Raman spectroscopies demonstrate the significant H{sub 2} annealing effect on the structural properties of ZnCoO/MoS{sub 2} hybrid. The interplay between the electron interaction at the interface and oxygen vacancies of ZnCoO can be responsible for the magnetic properties of the ZnCoO/MoS{sub 2} hybrid. The tunable magnetic properties have a promising application in multifunctional MoS{sub 2}-based semiconductor and spintronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Influence of Mn Doping on Structural, Photoluminescence and Magnetic Characteristics of Covellite-Phase CuS Nanoparticles

In the era of modern technology, the development of spintronic devices using diluted magnetic semiconductor nanoparticles has drawn significant attention from the world researchers. In this work, we report on novel Cu{sub 1−x}Mn{sub x}S (x = 0.00, 0.01, 0.03 and 0.05) compounds synthesized at room temperature through a simple precipitation method via EDTA as a capping agent. XRD patterns suggested that the entire synthesized nanoparticles exhibit covellite-phase hexagonal configuration like CuS. Reflectance measurements indicated energy band gap reduction by augmentation of Mn content. Photoluminescence spectra of prepared nanoparticles showed strong blue, green and weak yellow emissions at 471, 533 and 583 nm, respectively. The room-temperature VSM measurements suggested that bare CuS showed a diamagnetic nature, while Mn-doped CuS nanoparticles exhibited paramagnetism, which is enhanced with increasing Mn dopant concentration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Density Functional Study of Half-Metallic Ferromagnetism in the New Heusler Compounds CaYO{sub 2} (Y = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn)

The structural, electronic, and magnetic properties of full-Heusler alloys CaYO{sub 2} (Y = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) were investigated using full-potential linearized augmented plane wave method based on density functional theory. It was confirmed that these compounds can be synthesized experimentally due to their negative formation energies. The results predicted that all compounds in AlCu{sub 2}Mn-type structure were more stable than CuHg{sub 2}Ti-type structure. The band structure calculations showed that alloys CaYO{sub 2} (Y = Cr, Fe, Ni, and Cu) in AlCu{sub 2}Mn-type structure and CaYO{sub 2} (Y = Ti, V, Cr, Co, and Ni) in CuHg{sub 2}Ti-type structure have half metallic behavior. The origin of half-metallic characteristic was investigated using electronic density of states for CaFeO{sub 2}. Among these alloys, CaCrO{sub 2} was half-metal in a wide range of lattice constants indicating its resistance against destructive factors of half-metallicity such as temperature and pressure. The total magnetic moments for half-metallic alloys were integer values and obeyed the Slater-Pauling rules. The CaYO{sub 2} alloys with half-metallic character may be good candidates for practical applications in spintronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Lateral Shifts for Spin Electrons in a Hybrid Magnetic-Electric-Barrier Nanostructure Modulated by Spin-Orbit Couplings

We theoretically investigate how to modulate spin-dependent lateral shifts by the spin-orbit coupling (SOC) in a hybrid magnetic-electric-barrier (MEB) nanostructure, which can be experimentally realized by depositing a ferromagnetic (FM) stripe and a Schottky metal (SM) stripe on the top and bottom of the semiconductor heterostructure, respectively. Two kinds of ROCs, Rashba SOC (RSOC) and Dresselhaus SOC (DSOC), are taken into account fully. The Schrödinger equation of the spin electron in the hybrid MEB nanostructure is exactly solved by using the improved transfer-matrix method (ITMM), and the lateral shift and its spin polarization are numerically calculated with the help of the stationary phase method (SPM). Theoretical analysis indicates that the spin polarization effect in the lateral shift still exists in the hybrid MEB nanostructure when the SOCs are considered. Numerical simulations show that both magnitude and sign of the spin polarization effect in lateral shifts vary strongly with the strengths of RSOC and DSOC. These interesting features may offer an effective means to control the behavior of spin-polarized electrons in the semiconductor nanostructure, and such a hybrid MEB nanostructure serves as a SOC-manipulable spatial spin splitter for spintronic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

First-Principles Study in New Hf{sub 2}CoZ (Z = B, C, Al, Si, Ga, Ge, In, Sn, Tl, and Pb) Heusler Alloys

The full-potential linearized augmented plane wave method within density functional theory was used to investigate the electronic structures, magnetic properties, and half-metallicity in Hf{sub 2}CoZ (Z = B,C, Al, Si, Ga, Ge, In, Sn, Tl, and Pb) alloys with AlCu{sub 2}Mn- and CuHg{sub 2}Ti-type structures. The AlCu{sub 2}Mn-type structure is energetically favorable than the CuHg{sub 2}Ti-type structure for all compounds. Hf{sub 2}CoGa, Hf{sub 2}CoAl, Hf{sub 2}CoIn, Hf{sub 2}CoTl, and Hf{sub 2}CoSn compounds in the CuHg{sub 2}Ti-type structure were half-metallic ferromagnets. The d-d and covalent hybridizations between transition metals Hf and Co were effective in the formation of minority band gap. The total magnetic moments of half-metallic Hf{sub 2}CoZ (Z = Al, Ga, In, Sn, and Tl) compounds in the CuHg{sub 2}Ti-type structure obeyed the Slater–Pauling rule (M{sub tot} = Z{sub tot} − 18). Hf{sub 2}CoIn and Hf{sub 2}CoTl compounds were half-metals in relatively wide ranges of lattice constants which indicates that they can be promising and interesting candidates for spintronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Strain-Dependent Electronic and Magnetic of Mg-Doped Monolayer of WS{sub 2}

Magnetic properties of Mg-doped WS{sub 2} monolayer under strain are investigated by ab initio methods. Without strain, the Mg-doped WS{sub 2} monolayer is a magnetic nano material and the total magnetic moment is about 1.68 μ{sub B}. We applied strain to Mg-doped WS{sub 2} monolayer from −10 to 10%. The system changes from semiconductor to half-metallic material from 3 to 10% strain. The magnetic moment gets a maximum value of 2.07 μ{sub B} at −3% compressive strain. However, the magnetic moment of system decreases to zero sharply when compressive strain arrived at −5%. The coupling among the 3s states of Mg, 5d states of W, and 3p states of S is responsible for the strong strain effect on the magnetic properties. Our studies predict Mg-doped WS{sub 2} monolayer under strain to be candidates for application in spintronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Strain on Magnetic Coupling in Ga-Doped WS{sub 2} Monolayer: Ab Initio Study

Magnetic properties of Ga-doped WS{sub 2} monolayer under strain are investigated by ab initio methods. Without strain, the Ga-doped WS{sub 2} monolayer is a magnetic nanomaterial, and the total magnetic moment is about 0.82 μ{sub B}. We applied strain to Ga-doped WS{sub 2} monolayer from − 10 to 10%. The magnetic properties are modified under different strains, and a maximum magnetic moment reaches 3.09 μ{sub B} at − 3% compressive strain. However, the magnetic moment of system decreases to zero sharply when compressive strain arrived at − 10%. The coupling among Ga 3d, W 5d, and S 3p states is responsible for the strong strain effect on the magnetic properties. Our studies predict Ga-doped WS{sub 2} monolayer under strain to be candidates for application in spintronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Search for New Half-Metallic Ferromagnets in Quaternary Diamond-Like Compounds I–II{sub 2}–III–VI{sub 4} and I{sub 2}–II–IV–VI{sub 4} (I = Cu; II = Mn, Fe, Co; III = In; IV = Ge, Sn; VI = S, Se, Te)

The structural, electronic, and magnetic properties I–II{sub 2}–III–VI{sub 4} and I{sub 2}–II–IV–VI{sub 4} are investigated firstly by using the first-principles calculations. The investigation was done using the ab initio full-potential linearized augmented plane wave (FPLAPW) method where the exchange–correlation potential was calculated with the frame of GGA and GGA+U. The theoretically predicted lattice parameters for I–II{sub 2}–III–VI{sub 4} and I{sub 2}–II–IV–VI{sub 4} alloys are in good agreement with existing experimental measurements. The possibility of half-metallic ferromagnetism in I–II{sub 2}–III–VI{sub 4} and I{sub 2}–II–IV–VI{sub 4} (I = Cu; II = Mn, Fe, Co; III = In; IV = Ge, Sn; VI = S, Se, Te) was analyzed by electronic band structure and density of states calculations. We found that Cu{sub 2}CoGeS{sub 4}, Cu{sub 2}FeGeS{sub 4}, Cu{sub 2}FeSnS{sub 4}, and CuMn{sub 2}InSe{sub 4} compounds exhibit a complete half-metallic characteristic with a total spin moment of 3.00, 4.00, 4.00, and 10.00 μ{sub B} and direct band gap of (Eg ↑ = 0.63 eV), (Eg ↑ = 0.90 eV), (Eg ↑ = 0.31 eV), and (Eg ↓ = 1.10 eV), respectively. These results may be of interest for spintronic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Study of the Electronic Structure, Magnetic and Elastic Properties and Half-Metallic Stability on Variation of Lattice Constants for CoFeCrZ (Z = P, As, Sb) Heusler Alloys

Structural, elastic, magnetic and electronic properties of CoFeCrZ (Z = P, As, Sb) Heusler alloys in their YI-type structure have been computed by density functional theory-based WIEN2k code within generalized gradient approximation for exchange correlation functions. Values of formation energy and elastic constants verify the stability of these alloys. True half metallic ferromagnetic behaviour with 100% spin polarization and good band gap in the minority spin are obtained for all the alloys. Magnetic moment of these alloys is 4.00 μ{sub B}, which matches well with the value predicted from Slater-Pauling rule. Half-metallicity is maintained over a wide range of lattice constants making these alloys promising for spintronics device applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Ab Initio Study of Magnetism in Nonmetal Adsorption on Arsenene Monolayer

The structural, electronic, and magnetic properties of adsorbed arsenene monolayer with a series of nonmetal atoms, including B, C, F, N, and O, are systematically investigated using first-principles calculations. Nonmagnetic behavior shows in the B-, F-, N-, and O-adsorbed systems. The magnetism has been observed in the case of C, which originated from the 2p electrons of C and its neighboring As 4p states. Meanwhile, these nonmagnetic elements can induce impurity channels around Fermi level, which reduce band gap of the systems. It implies that the B-, F-, N-, and O-adsorbed arsenene tune into narrow gap semiconductors without magnetic character. The X-adsorbed (X = B, C, F, N, and O) arsenene systems are promising candidates for spintronic devices in the future.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Ab Initio Theoretical Prediction of Structural, Electronic, and Magnetic Properties in the 3d (Mn)-Doped Zinc-Blende MgSe: A DFT-mBJ Approach

In this paper, we have investigated the structural, electronic, and magnetic properties of magnesium selenium (MgSe) doped with transition metal manganese (Mn) impurity in the cubic diluted magnetic semiconductor (DMS) zinc blende structure. The compounds which we are interested are as Mg{sub 1−x}Mn{sub x}Se where x change between 0 and 1 by step 0.25. All properties are studied, using first-principles calculation of density functional theory under the framework of the full-potential linearized augmented plane waver (FP-LAPW). In our study, we employed the Wu-Cohen generalized approximation (WC-GGA) to optimize the crystal structure, whereas Tran-Blaha modified Becke-Johnson potential (TB-mBJ) as a new functional was applied to compute the electronic and magnetic properties in order to get some better degree of precision. The electronic band structures and density of state plots reveal ferromagnetic semiconducting behavior in these compounds, and the exchange constants N{sub 0}α and N{sub 0}β are calculated to validate the effects resulting from exchange splitting process. Moreover, for each concentration x, the value of total magnetic moment has been estimated to equal to 5 μ{sub B}. The important magnetic moments values obtained in these compounds indicate the potential for their use in spintronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

High-Pressure and Temperature Dependence of Electronic, Magnetic, Elastic, Thermodynamic, and Transport Properties of Full-Heusler Alloys Co{sub 2}YIn (Y = Nb, Zr)

Structural, elastic, magnetic, and electronic properties of Co{sub 2}YIn (Y = Nb, Zr) have been investigated by means of the full-potential linearized augmented plane wave along with generalized gradient approximation + U/modified Becke-Johnson method in the stable Fm-3m phase. The optimized equilibrium lattice parameter in stable phase is 6.1744 Å for Co{sub 2}NbIn and 6.2824 Å for Co{sub 2}ZrIn. We have calculated the spin-resolved density of states for both the alloys to show that the ferromagnetic behavior of Co{sub 2}NbIn is due to the exchange splitting of Co and Nb atoms and due to Co and Zr in Co{sub 2}ZrIn. In spin-up configuration, there is absence of energy gap while an energy gap can be seen in spin-down state for both the alloys exhibiting a half-metallic character. Through the elastic constants and their discussions, we have predicted the elastic behavior of the materials. The quasi-harmonic approximations have been employed to study the pressure- and temperature-dependent thermodynamic properties. The Boltzmann theory is employed to investigate the electronic transport properties of these alloys. The defined material properties may pay as a prime stand for the application of material in spintronics and thermoelectrics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗