Structural,electronic, and magnetic properties of transition metal doped ReS<Subscript>2</Subscript> monolayer

Magnetic properties of transition-metal (TM) atoms (TM = Co, Cu, Mn, Fe, and Ni) doped ReS₂ monolayer are investigated by ab initio calculations. It is found that magnetism appears in the cases of Co, Fe, and Ni. Among all the samples, the Co-doped system has the largest magnetic moment. Therefore, we further study the interaction in the two-Co-doped system. Our results show that the interaction between two Co atoms is always ferromagnetic (FM), but such FM interaction is obviously depressed by the increasing Co–Co distance, which is well described by a simple Heisenberg model based on the Zener theory. Our results provide useful insight for promising applications of TM-doped ReS₂ monolayer in the future.     

Electronic structures,magnetic properties and band alignments of 3d transition metal atoms doped monolayer MoS2

Utilizing first-principles calculations, the electronic structures, magnetic properties and band alignments of monolayer MoS₂ doped by 3d transition metal atoms have been investigated. It is found that in V, Cr, Mn, Fe-doped monolayers, the nearest neighboring S atoms (S_NN) are antiferromagnetically polarized with the doped atoms. While in Co, Ni, Cu, Zn-doped systems, the S_NN are ferromagnetically coupled with the doped atoms. Moreover, the nearest neighboring Mo atoms also demonstrate spin polarization. Compared with pristine monolayer MoS₂, little change is found for the band edges' positions in the doped systems. The Fermi level is located in the spin-polarized impurity bands, implying a half-metallic state. These results provide fundamental insights for doped monolayer MoS₂ applying in spintronic, optoelectronic and electronic devices.     

A first-principle prediction on the magnetism and electronic structure of Ti-doped CoO with two O vacancies

The electronic structure and magnetism in Co₁₄Ti₂O₁₄ systems are investigated by using the first-principles calculations. The system of 2 × 2 × 2 Co₁₄Ti₂O₁₆ supercell doped with Ti at 9 and 11 position shows a half-metallic character with a high spin polarization. Based on the above system, we remove two O atoms to form two O vacancies. The two O vacancies near Ti have a huge effect on the electronic structure and magnetic properties of Co₁₄Ti₂O₁₄ system. When O vacancies locate at 1 and 3 positions, the system shows a half-metallic character. For the O vacancies at 6 and 8 positions, the system shows a semiconducting character. The system with O vacancies at 9 and 11 positions is a typical spin gapless semiconductor.     

Prediction of Interesting Ferromagnetism in Janus Semiconducting Cr2AsP Monolayer

2D half-metallic materials that have sparked intense interest in advanced spintronic applications are essential to the developing next-generation nanospintronic devices. This study has adopted a first-principles calculation method to predict the magnetic properties of intrinsic, Se-doped, and biaxial strain tuning Cr₂AsP monolayer. The Janus Cr₂AsP monolayer is proven to be an intrinsic ferromagnetic (FM) semiconductor with an exchange splitting bandgap of 0.15 eV at the PBE+U level. Concentration-dependent Se doping, such as Cr₂As${}_{1-x}$Se_xP (x = 0.25, 0.50, 0.75), can regulate Cr₂AsP from FM semiconductor to FM half-metallicity. Specifically, the spin-up channel crosses the Fermi level, while the spin-down channel has a bandgap. More interestingly, the wide half-metallic bandgaps and spin bandgaps make them have important implications for the preparation of spintronic devices. At last, it also explore the effect of biaxial strain from -14% to 10% on the magnetism of the Cr₂AsP monolayer. There appears a transition from FM to antiferromagnetic (AFM) at a compressive strain of -10.7%, originating from the competition between the indirect FM superexchange interaction and the direct AFM interaction between the nearest neighboring Cr atoms. Additionally, when the compressive strain is -2% or the tensile strain is 6%, the semiconducting Cr₂AsP becomes a half-metallic material. These charming properties render the Janus Cr₂AsP monolayer with great potential for applications in spintronic devices.     

Electronic and magnetic properties of 3d-metal trioxides superhalogen cluster-doped monolayer MoS2: A first-principles study

Utilizing first-principle calculations, the structural, electronic, and magnetic properties of monolayer MoS₂ doped with 3d transition-metal (TM) atoms and 3d-metal trioxides (TMO₃) superhalogen clusters are investigated. 3d-metal TMO₃ superhalogen cluster-doped monolayers MoS₂ almost have negative formation energies except CoO₃ and NiO₃ doped monolayer MoS₂, which are much lower than those of 3d TM-doped structures. 3d-metal TMO₃ superhalogen clusters are more easily embedded in monolayer MoS₂ than 3d-metal atoms. MnO₃, FeO₃, CoO₃, and NiO₃ incorporated into monolayer MoS₂ are magnetic, and the total magnetic moments are approximately 1.0, 2.0, 3.0, and 4.0 μB per supercell, respectively. MnO₃ and FeO₃ incorporated into monolayer MoS₂ become semiconductors, whereas CoO₃ and NiO₃ incorporated into monolayer MoS₂ become half-metallic. Our studies demonstrate that the half-metallic ferromagnetic nature of 3d-metal TMO₃ superhalogen clusters-doped monolayer MoS₂ has a great potential for MoS₂-based spintronic device applications.     

Theoretical study of the magnetic interaction of Cr-doped ZnO with and without vacancies

First-principles density-functional theory (DFT) calculations have been performed to study the magnetic properties of ZnO:Cr with and without vacancies. The results indicate that the doping of Cr in ZnO induces obvious spin polarization around the Fermi level and a total magnetic moment of 3.77μ_B. The ferromagnetism (FM) exchange interaction between Cr atoms is short-ranged and decreases with increasing Cr separation distance. It is suggested that the FM state is not stable with low concentration of Cr. The presence of O vacancies can make the half-metallic FM state of the system more stable, so that higher Curie temperature ferromagnetism may be expected. Nevertheless, Zn vacancies can result in the FM stability decreasing slightly. The calculated formation energy shows that V_Zn+Cr_Zn complex forms spontaneously under O-rich conditions. However, under Zn-rich conditions, the complex of V_O+Cr_Zn forms more easily. Thus, ZnO doped with Cr may exhibit a concentration of vacancies that influence the magnetic properties.     

Modulation of magnetic properties of bilayer SnSe with transition-metals doping in the interlayer

We investigate the spin-polarized electronic and magnetic properties of bilayer SnSe with transition-metal (TM) atoms doped in the interlayer by using a first-principles method. It shows that Ni dopant cannot induce the magnetism in the doped SnSe sheet, while the ground state of V, Cr, Mn, Fe and Co doped systems are magnetic and the magnetic moment mainly originates from 3d TM atom. Two types of factors, which reduce the magnetic moment of TM atoms doped in bilayer SnSe, are identified as spin-up channel of the 3d orbital loses electrons to SnSe sheet and spin-down channel of the 3d orbital gains electrons from 4s orbital. The spin polarization is found to be 100% at Fermi level for the Mn and Co atoms doped system, while the Ni-doped system is still a semiconductor with a gap of 0.26 eV. These results are potentially useful for development of spintronic devices.     

Half-metallic ferrimagnetism in Full-Heusler alloy Mn2CuMg

In the paper Ab initio electronic structure calculations are applied to study the electronic structure and magnetism properties of a new Mn-based Heusler alloy Mn₂CuMg. We take into account both possible L 2₁ structures (CuHg₂Ti and AlCu₂Mn types). The CuHg₂Ti-type structure is found to be energetically more favorable than the AlCu₂Mn-type structure and presents half-metallic ferrimagnetism. However, the case of exchanging X with Y atoms in generic formula loses its half-metallicity due to the symmetric surroundings. Calculations show that their total spin moment is −1μ_B for a wide range of equilibrium lattice constants and the total spin magnetic moment is attributed mainly to the two Mn atoms, while the Cu atom is almost non-magnetic. A small total spin moment origins from the antiparallel configurations of the Mn partial moments. The CuHg₂Ti-type Mn₂CuMg alloy keeps a 100% of spin polarization of conduction electrons at the Fermi level, thus opening the way to engineer new half-metallic alloys with the desired magnetic properties.     

Computationally predicting spin semiconductors and half metals from doped phosphorene monolayers

First-principles computations are performed to investigate phosphorene monolayers doped with 30 metal and nonmetal atoms. The binding energies indicate the stability of all doped configurations. Interestingly, the magnetic atom Co doping induces the absence of the magnetism while the magnetism is realized in phosphorene with substitutional doping of nonmagnetic atoms (O, S, Se, Si, Br, and Cl). The magnetic moment of transition metal (TM)-doped systems is suppressed in the range of 1.0-3.97 μ_B. The electronic properties of the doped systems are modulated differently; O, S, Se, Ni, and Ti doped systems become spin semiconductors, while V doping makes the system a half metal. These results demonstrate potential applications of functionalized phosphorene with external atoms, in particular to spintronics and dilute magnetic semiconductors.     

Half-metallicity and magnetism of the quaternary inverse full-Heusler alloy Ti<Subscript>2-x</Subscript>M<Subscript>x</Subscript>CoAl (M = Nb,V) from the first-principles calculations

Using the first-principles calculations based on density functional theory, we investigate the more d-electrons doping effects on the electronic structure and magnetism of the parent inverse Heusler alloy Ti₂CoAl by the substitution of Nb and V atoms for Ti(A) and Ti(B) atoms locating at the two inequivalent sublattices. The Ti₂CoAl is half-metallic with Fermi level near the top of the minority-spin valence band and hence its spin-polarization is easily reduced by the spin-flip excitation. Our total energy calculations show that the V/Nb doping at the Ti(A)/Ti(B) site is energetically favorable compared with the Ti(B)/T(A) site due to the lower total energy. Our band structure calculations indicate that for the V doped compounds, half-metallicity can be well retained regardless of doping sites and percentages except for the case of Ti(A)-site doping with x = 1, while for Nb doped compounds, the half-metallicity persists only in Ti(B)-site doping with different percentages. For the doped compounds with half-metallicity, the Fermi level shifts from the top of minority-spin valence band to the bottom of minority-spin conduction band with increasing content of x, and typically, the doped compounds (V in Ti(A) and Ti(B) sites at x = 0.75 and 0.5, respectively; Nb in Ti(B) site at x = 0.5), whose Fermi levels are adjusted to the expected positions to effectively inhibit the spin-flip excitation are promising candidates for spintronics applications.     

TM掺杂的Ⅲ-Ⅴ族稀磁半导体电磁性质的第一原理计算

使用基于自旋局域密度泛函理论的第一性原理方法对3d过渡金属(TM=V，Cr，Mn，Fe，Co和Ni)掺杂的Ⅲ-Ⅴ族半导体(GaAs和GaP)的电磁性质进行了计算.结果发现：用V，Cr和Mn掺杂时体系将出现铁磁状态，而Fe掺杂时将出现反铁磁状态，Co和Ni掺杂时，其磁性则不稳定.其中，Cr掺杂的GaAs和GaP将可能是具有较高居里温度的稀磁半导体(DMS).在这些DMS系统中，V离子的磁矩大于理论期待值，Fe，Co和Ni离子的磁矩小于理论期待值，Cr和Mn离子的磁矩与期待值的差距取决于晶体的对称性以及磁性离子的能带分布.此外，使用Si和Mn共同对Ⅲ-Ⅴ族半导体进行掺杂，将有利于DMS表现为铁磁状态，并可以使体系的T_C进一步提高. 关键词： 稀磁半导体 过渡金属 掺杂 共掺杂     

First-principles investigation on the interlayer doping of SnSe<Subscript>2</Subscript> bilayer

Using density functional theory calculations, we systematically investigated the effects of numbers and types of transition metals (TM) on the magnetic property of SnSe₂ bilayer nanosheet. Our results revealed that, when one TM is introduced into the interlayer, the magnetic moment induced by the Co and Ni is tiny while it is largely strengthened with the doping of V, Cr, Mn, and Fe. When two TMs are inserted into the interlayer, V and Cr make the system change into a weak antiferromagnetism (AFM) state while Mn-, Fe-, Co-doped systems display a weak ferromagnetism (FM) ground state. These FM states have the magnetic moments which double those of the one TM–doping systems. With the TM numbers further increasing to four, the robust AFM and FM features appear with the doping of Fe and Mn, respectively. Ni cannot induce any magnetism whatever the numbers of Ni are filling in. Interestingly, with the increase of the numbers of dopants, transitions from FM to AFM and AFM to FM are predicted to be realized on Fe-SnSe₂ and Cr-SnSe₂ systems, respectively. This kind of transition may be important for the applications in spintronic devices.

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The electronic structure and magnetic properties of metallic antiferromagnetic Co[(CH3PO3)(H2O)] studied by first-principles calculations

The electronic structure, the metallic and magnetic properties of metal phosphonate Co[(CH₃PO₃)(H₂O)] have been studied by first-principles calculations, which were based on the density-functional theory (DFT) and the full potential linearized augmented plane wave (FPLAPW) method. The total energy, the spin magnetic moments and the density of the states (DOS) were all calculated. The calculations reveal that the compound Co[(CH₃PO₃)(H₂O)] has a stable metallic antiferromagnetic (AFM) ground state and a half-metallic ferromagnetic (FM) metastable state. Based on the spin distribution obtained from calculations, it is found that the spin magnetic moment of the compound is mainly from the Co²⁺, with some small contributions from the oxygen, carbon and phosphorus atoms, and the spin magnetic moment per molecule is 5.000μ_B, which is in good agreement with the experimental results.     

First-principles study on the magnetism and electronic structure in 3d transition metal (X=Sc,V, Cr,Mn, Fe,Ni, Cu) doped CoO

We have studied the electronic structure and magnetism of the single transitional metal element X=Sc, V, Cr, Mn, Fe, Ni, Cu-doped CoO systems by first-principles calculations. At X=Sc, Cr, Cu, the binding energy of the doped systems is lower than pure CoO, suggesting that these systems are energetically stable. In the Sc, V, Cr, Mn, Fe, Ni, Cu-doped 2×2×2 CoO supercells, the total magnetic moments are 3.03, 5.64, 6.80, 7.70, 6.93, 2.30 and 1.96 μ_B, respectively. At X=Cr and Fe, the doped CoO systems are half-metallic with a high spin polarization. The large magnetic moment and high spin polarization in the Cr and Fe-doped CoO are important for the design of the spintronic devices.     

Nitrogen and Boron substitutional doped zigzag silicene nanoribbons: Ab initio investigation

We performed a spin polarized density-function theory study of the stabilities, electronic and magnetic properties of zigzag silicene nanoribbons (ZSiNRs) substitutionally doped with a single N or B atom located at various sites ranging from edge to center of the ribbon. From minimization of the formation energy, it is found that the substitutional doping is favorable at edge of the ribbon. A single N or B atom substitution one edge Si atom of ZSiNRs can greatly suppress the spin-polarizations of the impurity atom site and its vicinity region, and leads to a transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state, which is attributed to the splitting of the original spin degenerate edge bands. A single N atom doped ZSiNRs still keep semiconductor property but a single B atom doped ZSiNRs exhibit a half-metallic character. Our results reveal that substitution doped ZSiNRs have potential applications in Si-based nanoelectronics, such as field effect transisitors (FETs), negative differential resistance (NDR) and spin filter (SF) devices.     

Electronic and magnetic properties of Mn-doped WSe2 monolayer under strain

Electronic and magnetic properties of Mn-doped WSe₂ monolyer subject to isotropic strain are investigated using the first-principles methods based on the density functional theory. Our results indicate that Mn-doped WSe₂ monolayer is a magnetic semiconductor nanomaterial with strong spontaneous magnetism without strain and the total magnetic moment of Mn-doped system is 1.038μ_B. We applied strain to Mn-doped WSe₂ monolayer from -10% to 10%. The doped system transforms from magnetic semiconductor to half-metallic material from −10% to −2% compressive strain and from 2% to 6% tensile strain. The largest half-metallic gap is 0.450 eV at −2% compressive strain. The doped system shows metal property from 7% to 10%. Its maximum magnetic moment comes to 1.181μ_B at 6% tensile strain. However, the magnetic moment of system decreases to zero sharply when tensile strain arrived at 7%. Strain changes the redistribution of charges and arises to the magnetic effect. The coupling between the 3d orbital of Mn atom, 5d orbital of W atom and 4p orbital of Se atom is analyzed to explain the strong strain effect on the magnetic properties. Our studies predict Mn-doped WSe₂ monolayers under strain to be candidates for thin dilute magnetic semiconductors, which is important for application in semiconductor spintronics.     

Half-metallic ferrimagnetism in Mn2CuGe

We study magnetism properties and the electronic structure of a new Mn-based Heusler alloys Mn₂CuGe using ab initio electronic structure calculations. We take into account both possible L 2₁ structures (CuHg₂Ti and AlCu₂Mn types). The CuHg₂Ti-type structure is found to be energetically more favorable than the AlCu₂Mn-type structure and exhibits half-metallic ferrimagnetism. Calculations show that their total spin moment is for a wide range of equilibrium lattice constants and magnetic moment mainly comes from the two Mn atoms, while the Cu atom is almost nonmagnetic. The small total moment comes from the antiparallel configurations of the Mn partial moments. And the CuHg₂Ti-type Mn₂CuGe alloy keeps a 100% of spin polarization at the Fermi level. Thus, the Mn₂CuGe is the compound of choice for further experimental investigations.     

V,Cr,Mn掺杂MoS2磁性的第一性原理研究

基于第一性原理的自旋极化密度泛函理论分别研究了过渡金属V, Cr, Mn掺杂单层MoS₂的电子结构、 磁性和稳定性. 结果表明: V和Mn单掺杂均能产生一定的磁矩, 而磁矩主要集中在掺杂的过渡金属原子上, Cr单掺杂时体系不显示磁性. 进一步讨论双原子掺杂MoS₂ 体系中掺杂原子之间的磁耦合作用发现, Mn掺杂的体系在室温下显示出稳定的铁磁性, 而V掺杂则表现出非自旋极化基态. 形成能的计算表明Mn掺杂的MoS₂体系相对V和Cr 掺杂结构更稳定. 由于Mn掺杂的MoS₂ 不仅在室温下可以获得比较好的铁磁性而且其稳定性很高, 有望在自旋电子器件方面发挥重要的作用. 关键词： 2')" href="#">单层MoS₂ 掺杂 铁磁态 第一性原理     

Manipulating electronic and magnetic properties of black phosphorene with 4d series transition metal adsorption

We carry out first-principles calculations within density-functional theory to investigate the structural, electronic and magnetic properties of 4d transition metal (TM) decorated monolayer black phosphorene (BP). The results indicate that the TM adsorption on BP can have dilute magnetic semiconductor (DMS) properties. The spin polarized semiconducting state is realized in BP by adsorption of Y, Nb and Ru, while a half-metal state is obtained by Tc adsorption. In the case of two same types of TMs adsorption on BP, only [email protected] shows DMS state. In particular, two different types of TMs decorated BP can induce magnetic moments, localized mainly on the 4d TMs and the neighboring P atoms. Furthermore, the 4d TMs may enrich the electronic properties of BP, such as half-metallic, metallic and semiconducting features. These findings suggest that the 4d TM adsorbed BP can be used as a potential next-generation spintronics and magnetic storage material.     

双轴应变调控二维单层C2X2TM（X = O, H; TM=Fe, Cr） 的多铁性研究

基于密度泛函理论的第一性原理计算,系统地研究了过渡金属原子插层的单层氧化/氢化石墨烯的磁学性质和铁电性质.在考虑了电子在位库仑作用和自旋轨道耦合作用下,得到了过渡金属Fe、Cr插层形成的C₂X₂TM二维单层膜的稳定结构以及基态磁性结构,研究了不同应变作用下C₂X₂TM的磁性、能带、铁电极化以及电子结构的变化.结果发现,对于任何应变下的C₂X₂TM其基态磁性都为手性逆时针反铁磁结构.在无应变时体系存在一个较大的离子翻转势垒,通过外加双轴应变,可有效调控体系的势垒高度和能隙,发现25%应变下C₂O₂Cr和30%应变时C₂O₂Fe单层薄膜具有与GeS等二维铁电材料相近的铁电极化和翻转势垒,这些研究结果表明C₂O₂Fe(Cr)单层薄膜是一种新型二维多铁性材料.