Mn Monolayer Research Articles

Modeling the manganese deposit on the BP (111)-(2×2) surface: Density functional theory studies

The structural, electronic, and magnetic properties of the manganese (Mn) adsorption and incorporation into the boron phosphide (BP) in surface (111) – periodicity (2 × 2) structure have been investigated using spin-polarized first-principles total-energy calculations. The exchange-correlation energies are treated within the generalized gradient approximation. The magnetic properties have been studied by considering different coverages and magnetic configurations. The Mn adsorption and incorporation range from ¼ to 1 monolayer (ML), with results displaying: Ferromagnetic (FM), antiferromagnetic (AFM), and non-magnetic (NM) behavior at low, intermediate, and high coverages, respectively. The electronic properties are explored considering the total density of states (DOS) and the projected density of states (PDOS). It is noted that the contribution of the Mn-d orbital modifies the metallicity of the surface. The results show that the most favorable structure is the 1 Mn ML adsorption, with an AFM alignment and a magnetic moment of 0 μB/atom. The material exhibits metallicity at the first monolayer induced by manganese, while the lower internal layers are semiconductors. Finally, the charge density distribution corroborates the surface metallic phase, which indicates that the proposed material can be helpful in the design of new spintronic devices.

First-Principles Analysis of Lattice Thermal Conductivity in Monolayer Mn2C

First-Principles Analysis of Lattice Thermal Conductivity in Monolayer Mn₂C

Solid State Reaction Epitaxy, A New Approach for Synthesizing Van der Waals heterolayers: The Case of Mn and Cr on Bi2Se3

AbstractVan der Waals (vdW) heterostructures that pair materials with diverse properties enable various quantum phenomena. However, the direct growth of vdW heterostructures is challenging. Modification of the surface layer of quantum materials to introduce new properties is an alternative process akin to solid state reaction. Here, vapor deposited transition metals (TMs), Cr and Mn, are reacted with Bi2Se3 with the goal to transform the surface layer to XBi2Se4 (X = Cr, Mn). Experiments and ab initio MD simulations demonstrate that the TMs have a high selenium affinity driving Se diffusion toward the TM. For monolayer Cr, the surface Bi2Se3 is reduced to Bi2‐layer and a stable (pseudo) 2D Cr1+δSe2 layer is formed. In contrast, monolayer Mn can transform upon mild annealing into MnBi2Se4. This phase only forms for a precise amount of initial Mn deposition. Sub‐monolayer amounts dissolve into the bulk, and multilayers form stable MnSe adlayers. This study highlights the delicate energy balance between adlayers and desired surface modified layers that governs the interface reactions and that the formation of stable adlayers can prevent the reaction with the substrate. The success of obtaining MnBi2Se4 points toward an approach for the engineering of other multicomponent vdW materials by surface reactions.

Carrier doping modulates the magnetoelectronic and magnetic anisotropic properties of two-dimensional MSi2N4 (M = Cr, Mn, Fe, and Co) monolayers.

Through extensive density functional theory (DFT) calculations, our investigation delves into the stability, electrical characteristics, and magnetic behavior of monolayers (MLs) of MSi2N4. Computational analyses indicate intrinsic antiferromagnetic (AFM) orders within the MSi2N4 MLs, as a result of direct exchange interactions among transition metal (M) atoms. We further find that CrSi2N4 and CoSi2N4 MLs with primitive cells (pcells) exhibit half-metallic properties, with respective spin-β electron gaps of 3.661 and 2.021 eV. In contrast, MnSi2N4 and FeSi2N4 MLs with pcells act as semiconductors, having energy gaps of 0.427 and 0.282 eV, respectively. When the SOC is considered, the CrSi2N4, MnSi2N4 and FeSi2N4 MLs are metals, while the CoSi2N4 ML is a semiconductor. Our findings imply the dynamics and thermodynamic stability of MSi2N4 MLs. We have also explored the influence of carrier doping on the electromagnetic attributes of MSi2N4 MLs. Interestingly, charge doping could transform CrSi2N4, MnSi2N4, and CoSi2N4 MLs from their original AFM state into a ferromagnetic (FM) order. Moreover, carrier doping transformed CrSi2N4 and CoSi2N4 MLs from spin-polarized metals to half-metals (HMs). It is of particular note that doping of CrSi2N4 MLs with +0.9 e per pcell or more holes caused a switch in the easy axis (EA) to the [001] axis. The demonstrated intrinsic AFM order, excellent thermodynamic and kinetic stability, adjustable magnetism, and half-metallicity of the MSi2N4 family suggest its promising potential for applications in the realm of spintronics.

Tuning the magnetic properties of double transition-metal carbide CoMC (M = Ti, V, Cr, Mn, Fe, Ni) monolayers.

The intrinsic ferromagnetism of two-dimensional transition metal carbide Co2C is remarkable. However, its practical application in spintronic devices is encumbered by a low Curie temperature (TC). To surmount this constraint, double transition-metal carbide CoMC (M = Ti, V, Cr, Mn, Fe, Ni) monolayers are constructed with the aim of improving the magnetic properties and Curie temperature of Co2C. The magnetic properties of CoMC monolayers are comprehensively investigated by first-principles calculations and the effects of hole doping and biaxial strain on the magnetic properties of CoMC (M = V, Cr, Mn) monolayers are also studied. The ground states of CoTiC, CoMnC and CoNiC monolayers all favor ferromagnetic ordering, whereas the CoVC and CoCrC monolayers favor antiferromagnetic ordering and the CoFeC monolayer is non-magnetic. Excitedly, the CoMnC monolayer displays a high total magnetic moment of 4.024μB and a TC of 1366 K. Moreover, the control of hole doping can effectively improve the TC of CoVC, CoCrC, and CoMnC monolayers to 680, 1317, 3044 K, respectively. Finally, applying the in-plain biaxial strain, the CoVC monolayer can be transformed into a ferromagnetic semiconductor under a tensile strain of 6%. The TC values of CoVC, CoCrC, and CoMnC monolayers are tuned by biaxial strain to 440, 1334 and 2390 K, respectively. Their TC above room temperature demonstrates that these monolayers have potential applications in spintronic devices. These theoretical investigations provide valuable insights into guiding experimental synthesis endeavors.

Proposals for gas-detection improvement of the FeMPc monolayer towards ethylene and formaldehyde by using bimetallic synergy.

Development and fabrication of a novel gas sensor with superb performance are crucial for enabling real-time monitoring of ethylene (C2H4) and formaldehyde (H2CO) emissions from industrial manufacture. Herein, first-principles calculations and AIMD simulations were carried out to investigate the effect of the Fe-M dimer on the adsorption of C2H4 and H2CO on metal dimer phthalocyanine (FeMPc, M = Ti-Zn) monolayers, and the electronic structures and sensing properties of the above adsorption systems were systematically discussed. The results show that the FeMPc (M = Ti, V, Cr, Mn) monolayers interact with C2H4 and H2CO by chemisorption except for the FeMnPc/H2CO system, while the other adsorption systems are all characterized by physisorption. Interestingly, the adsorption strength of C2H4 and H2CO can be effectively regulated by the bimetallic synergy of the Fe-M dimer. Moreover, the FeCrPc and FeMnPc monolayers exhibit excellent sensitivity towards C2H4 and H2CO, and have short recovery time (4.69 ms-2.31 s) for these gases at room temperature due to the effective surface diffusion at 300 K. Consequently, the FeCrPc and FeMnPc materials can be utilized as high-performance, reusable gas sensors for detecting C2H4 and H2CO, and have promising applications in monitoring the release of ethylene and formaldehyde from industrial processes.

Surface-strain-dependent room-temperature ferromagnetism in hexagonal MIn2S4 monolayers

The electronic occupation at 3d transition metal and crystal symmetry play a critical role in realizing spin polarization, but the weak spin exchange interaction makes it difficult to obtain room-temperature ferromagnetism, especially in two-dimensional (2D) materials. Different from traditional bulk phase with semiconducting feature, the free-standing hexagonal MIn2S4 (M = Fe, Co, Ni, Mn) monolayers are proposed to discuss the strain-dependent magnetic behavior, in which the 3d-orbital hybridization and charge transfer can be regulated by structural deformation to enforce their spin exchange interaction, finally leading to a room-temperature 2D magnetic characteristic. The calculations disclose that the structural deformation not only regulates the spin polarization feature but also leads to an electronic reconfiguration. Our findings provide a new insight into designing 2D spintronic devices by strain engineering in hexagonal MIn2S4 monolayers.

Magnetism and magnetic properties of 3d transition metal monolayer on Pd(1 0 0)

First-principles calculations based on density functional theory (DFT) are utilized to examine the effect of 3d transition metal (TM) monolayer on the Pd (001) substrate. Four transition metal (Cr, Mn, Fe, and Co) monolayers are investigated in the middle of a 1 × 1 × 7face-centered cubic supercell. Two different structures are considered, one with the TM monolayer sandwiched between the Pd atoms in the supercell creating a substrate-cap structure (Pd/TM/Pd), while the other structure is left uncapped (Pd/TM). We found that the magnetocrystalline anisotropy energy of the (Pd/TM/Pd) structure is more significant than the uncapped structure (Pd/TM). Furthermore, the ground state of the Cr and Mn monolayers is antiferromagnetic, while the ferromagnetic ordering is the ground state for the Fe and Co monolayers. In addition, magnetic moments, anisotropy field, and maximum energy products are studied.

A theoretical investigation on the two-dimensional Fe/Mn tricarbides (XC3) as promising electrode materials for lithium-ion batteries

2D materials have shown great potential for application in metal-ion batteries due to their promising ionic and electronic conductivity as well as large capacities. In this work, we explore transition metal tricarbides as electrode material to lithium-ion batteries (LIBs) by employing CALYPSO method to conduct a structure search and then perform the first-principles density functional theory (DFT) calculation to study their electronic structure, thermodynamic stability, lithium capacity, lithium diffusion barrier and open circuit voltage. A series of two-dimensional transition metal tricarbides XC3 (X = Fe, Mn) monolayer was obtained from the structure search and four of them (marked by m-XC3 and d-XC3, X = Fe, Mn) were found to possess good dynamical, mechanical and thermodynamic stability from DFT calculation. Further calculation of electronic structure revealed a metallic character for the m-XC3 and d-XC3 (X = Fe, Mn), which ensures good electronic conductivity as electrodes of LIBs. The predicted migration energy barriers of Li diffusion on d-FeC3, d-MnC3, m-FeC3 and m-MnC3 were 0.16 eV, 0.16 eV, 0.19 eV and 0.17 eV respectively, which ensures fast charging/discharging rate. Moreover, d-FeC3, d-MnC3, m-FeC3 and m-MnC3 monolayer were found to have low open-circuit voltage of 1.511 V, 1.423 V, 0.913 V and 0.728 V, which make them suitable for the anode material in LIBs. Finally, the FeC3 and MnC3 monolayer showed theoretical specific capacity of 874 mAhg−1 and 885 mAhg−1. The predicted superior performance of Li storage and transport make the XC3 (X = Fe, Mn) monolayers to be promising candidates as the anode material of LIBs.

Computational Screening of Two-Dimensional Metal-Organic Frameworks as Efficient Single-Atom Catalysts for Oxygen Reduction Reaction.

The development of efficient and inexpensive oxygen reduction reaction (ORR) catalysts is crucial for renewable energy technologies. Herein, using density functional theory (DFT) methods and microkinetic simulations, we systematically investigated the ORR catalytic performance of a series of 2D metal-organic frameworks M3 (HADQ)2 (HADQ=2,3,6,7,10,11-hexaamine dipyrazino quinoxaline). It shows that all 2D M3 (HADQ)2 (M=Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh and Pd) monolayers are metallic, due to π-conjugated crystal orbitals centered on the central metals and ligand N atoms. The catalytic activity of M3 (HADQ)2 depends on the binding strength between ORR intermediates and metal species, and can be tuned via changing the central metals. Among these candidates, Rh3 (HADQ)2 and Co3 (HADQ)2 show superior ORR performance to Pt (111) with high half-wave potentials of 0.99 and 0.93 V, respectively. Moreover, the screened two catalysts have excellent intermediate-tolerance ability for dynamic coverage of oxygenated species on the active sites. Our work provides a new path towards developing efficient ORR electrocatalysts.

Modulation of optical absorption properties of monolayer InSe by introducing intermediate impurity levels in the band gap

The geometry, formation energy, charge density difference, electronic property, work function and optical absorption capacity of transition metals (TM) doped monolayer InSe have been systematically study by first-principles study. TM atoms tend to substitute In atoms under Se-rich growth conditions. Meanwhile, impurity levels (ILs) appear in the band gaps of all TM doped InSe. Especially Mn doping causes the ILs to be located in the middle of the band gap, thus Mn doped monolayer InSe exhibit remarkable optical absorption in the energy range 1.24 ∼ 24.8 eV, which is related to the mechanism of ILs assisted electronic transitions.

Critical behavior and exchange splitting in the two-dimensional antiferromagnet Mn on Re(0001)

We investigated the temperature-dependent electronic structure of the antiferromagnetic fcc-monolayer Mn on Re(0001) using vacuum-ultraviolet momentum microscopy. At $T=25$ K the collinear, row-wise antiferromagnetic phase of the Mn monolayer results in a spin splitting of states. Density-functional theory, being in good agreement with the experimental results, reveals the spin and orbital projection of the observed electronic bands. The exchange split bands shift in opposite directions with increasing temperature, decreasing the exchange splitting of a pair of itinerant bands from $280\ifmmode\pm\else\textpm\fi{}10$ meV at 25 K down to $185\ifmmode\pm\else\textpm\fi{}10$ meV at the N\'eel temperature ${T}_{\text{N}}=75\ifmmode\pm\else\textpm\fi{}5$ K. The exchange splitting remains constant for $T>{T}_{\text{N}}$. The persisting exchange splitting is attributed to a remaining short-range, fluctuating antiferromagnetic order far above ${T}_{\text{N}}$.

Unraveling the Catalytic Performance of the Nonprecious Metal Single-Atom-Embedded Graphitic s-Triazine-Based C3N4 for CO2 Hydrogenation.

Graphitic carbon nitride (g-C3N4) is regarded as a promising potent photoelectrocatalyst for CO2 reduction. Here, extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations are performed to systematically explore the structural and electronic properties of nonprecious metal single-atom-embedded graphitic s-triazine-based C3N4 (M@gt-C3N4, M = Mn, Fe, Co, Ni, Cu, and Mo) monolayer materials and their catalytic performances as the single-atom catalysts (SACs) for CO2 hydrogenation to HCOOH, CO, and CH3OH. It is found that the atomically dispersed non-noble metal Mn, Fe, Co, and Mo sites anchored on gt-C3N4 can efficiently activate both H2 and CO2, and their coadsorbed state serves as a precursor to the hydrogenation of CO2 to different C1 products. Among these SACs (M@gt-C3N4, M = Mn, Fe, Co, and Mo), Co@gt-C3N4 was predicted to have the best catalytic performance for CO2 hydrogenation to C1 products, although their mechanistic details are somewhat different. The predicted energy barriers of the rate-determining steps for the conversion of CO2 into HCOOH, CO, and CH3OH on Co@gt-C3N4 are 0.58, 0.67, and 1.19 eV, respectively. The desorption of products is generally energy-demanding, but it can be facilitated remarkably by the subsequent adsorption of H2, which regenerates M@gt-C3N4 for the next catalytic cycle. The present study demonstrates that the catalytic performance of gt-C3N4 can be well regulated by embedding the non-noble metal single atom, and the porous gt-C3N4 is nicely suited for the construction of high-performance single-atom catalysts.

Nanoscale skyrmions on a square atomic lattice

Spin-polarized scanning tunneling microscopy has been applied to study noncollinear spin textures of a Mn monolayer on a fourfold symmetric W(001) substrate revealing a zero-field spin spiral ground state and two different types of rotational domain walls. With an applied magnetic field of 9 T, we observe a coexistence of the spin spiral and the skyrmion phase, even though a previous theoretical study reported that the phase transition occurs at 18 T. The skyrmions show a roughly hexagonal arrangement despite the square lattice symmetry of the W(001) substrate. Based on a reduced set of energy parameters, we are able to describe the experimental findings and to analyze the topological properties of the rotational domain walls.

A magnetic map of O/Fe/Mn/Fe(001) multilayer with DFT+U scheme

Zenia et al. (Surface Science 584 (2005) 146152) have shown that a Mn monolayer on Fe(001) is in-plane antiferromagnetic. They have also obtained a ferromagnetic as well as an antiferromagnetic coupling between Mn and Fe in the subsurface layer but those couplings are found higher in energy. When an oxygen monolayer is added this in-plane antiferromagnetic solution becomes unstable. Besides Meza-Aguilar and Demangeat (Eur. Phys. J. B 93 (2020) 107 have shown that the interlayer exchange coupling in Fe/Cr/Fe(001) can be modified by the inclusion of one monolayer of oxygen i.e. O/Fe/Cr/Fe(001). In the present communication, we study the magnetic stability of a Mn monolayer on Fe(001) and the interlayer exchange coupling in Fe/O/Mn/Fe(001) and O/Fe/Mn/Fe(001) multilayers with a DFT+U scheme. The Fe/O/Mn/Fe(001) multilayer is energetically clearly unstable and convergency leads to the displacement of the oxygen monolayer on top of the Fe surface atoms so that we restrict ourselves to the determination of the magnetic map of O/Fe/Mn/Fe(001). The interlayer exchange coupling in Fe/Mn/Fe(001) is modified by adding a monolayer of oxygen atoms on it. This is very similar to the result obtained recently on Fe/Cr/Fe(001) multilayers.

Distorted 3Q state driven by topological-chiral magnetic interactions

We demonstrate that topological-chiral magnetic interactions can play a key role for magnetic ground states in ultrathin films at surfaces. Based on density functional theory we show that significant chiral-chiral interactions occur in hexagonal Mn monolayers due to large topological orbital moments which interact with the emergent magnetic field. Due to the competition with higher-order exchange interactions superposition states of spin spirals such as the 2Q state or a distorted 3Q state arise. Simulations of spin-polarized scanning tunneling microscopy images suggest that the distorted 3Q state could be the magnetic ground state of a Mn monolayer on Re(0001).

Perpendicular magnetic anisotropy induced by NiMn-based antiferromagnetic films with in-plane spin orientations: Roles of interfacial and volume antiferromagnetic moments

Antiferromagnetic (AFM) thin films are promising materials for engineering the magnetic anisotropy of adjacent ferromagnetic (FM) films. In this work, we explored the effects of triggering perpendicular magnetic anisotropy (PMA) of FM films by applying a series of NiMn-based AFM films with in-plane-oriented spin structures. The vertically expanded face-centered tetragonal ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50}$ films alone could not induce PMA in Co/Ni films. By contrast, PMA was triggered through the application of Mn-rich NiMn alloy films or ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50}/1$-monolayer Mn $(\mathrm{Mn}/1\text{\ensuremath{-}}\mathrm{ML} {\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50})$ heterostructures. Detailed analyses of a series of samples indicated that two criteria must be met for a NiMn-based AFM film to trigger PMA in a neighboring FM film: (1) perpendicular interface crystalline anisotropy of interfacial uncompensated Mn moments must be established, and (2) strengthened lateral exchange coupling to volume AFM moments must be made. This paper clarifies how NiMn-based AFM films with in-plane-oriented AFM spin structures trigger the PMA of FM films, thus identifying a pathway to increase control over antiferromagnet-induced PMA through the interface/volume magnetic engineering of AFM layers.

Cr doped MN (M = In, Ga) monolayer: A promising candidate to detect and scavenge SF6 decomposition components

In this paper, the adsorption properties of Cr modified InN (Cr-InN) and GaN (Cr-GaN) monolayers to SF6 decomposed components were investigated based on the density functional theory (DFT). Results reveal that these two graphene-like materials exhibit strong adsorption capacity for the three decomposed species SO2, SOF2 and SO2F2. Remarkable adsorption energy, significant charge transfer and molecular deformation indicate the occurrence of chemisorption. The hybridization of atomic electron orbitals in the density of states calculation verifies the strong chemical interaction between the gases and two monolayers. According to this strong adsorption capacity, Cr-InN and Cr-GaN monolayers demonstrate their potential as gas Scavenger for removing SF6 decomposition products in the insulation equipment. Besides, the significant change in conductivity of the monolayer caused by gas adsorption makes it possible to explore gas sensors based on Cr-InN and Cr-GaN monolayer. This paper indicates that Cr-doped InN and GaN monolayers can be used as adsorbents and sensors to guard the operation status of SF6 insulation devices by detecting and scavenging SF6 decomposed components.

Spin-spiral state of a Mn monolayer on W(110) studied by soft x-ray absorption spectroscopy at variable temperature

The noncollinear magnetic state of epitaxial Mn monolayers on tungsten (110) crystal surfaces is investigated by means of soft x-ray absorption spectroscopy, to complement earlier spin-polarized STM experiments. X-ray absorption spectra (XAS), x-ray linear dichroism (XLD) and x-ray magnetic circular dichroism (XMCD) Mn L23-edge spectra were measured in the temperature range from 8 to 300 K and compared to results of fully-relativistic ab initio calculations. We show that antiferromagnetic (AFM) helical and cycloidal spirals give rise to significantly different Mn L23-edge XLD signals, enabling thus to distinguish between them. It follows from our results that the magnetic ground state of a Mn monolayer on W(110) is an AFM cycloidal spin spiral. Based on temperature-dependent XAS, XLD and field-induced XMCD spectra we deduce that magnetic properties of the Mn monolayer on W(110) vary with temperature, but this variation lacks a clear indication of a phase transition in the investigated temperature range up to 300 K - even though a crossover exists around 170 K in the temperature dependence of XAS branching ratios and in XLD profiles.

Fe(110)上のMnナノクラスターと単原子層島のSTM電子構造測定

Fe(110)上のMnナノクラスターと単原子層島のSTM電子構造測定