Total Magnetic Moment Research Articles

Growth pattern and electronic and magnetic properties of Cr-doped silver clusters.

Growth pattern and electronic and magnetic properties of Agn Cr (n = 1-16) clusters have been investigated via density functional theory (DFT) combined with CALYPSO structure search method. The optimized geometry shows that the growth of the global minimum structures of Agn Cr clusters have obvious rule. when n > 12, silver atoms grow around an icosahedron which is almost unchanged in each structure. Analyses of electronic properties indicate that the doped Cr atom can only enhance the stability of larger silver clusters. Optical absorption and photoelectron spectra of Agn Cr isomers have been predicted and can be used for their structural identification. The icosahedral Ag12 Cr cluster with large energy level gap can be seen as a superatom. The adsorption capacity of Cr atom in Agn Cr cluster to CO is much higher than that of free Cr atom. The intensity of IR and Ramam spectra can be dramatically enhanced when CO is absorbed on Agn Cr cluster that Cr atom is encapsulated by Ag atoms. Moreover, the red shift of IR and Raman spectra of CO adsorbed on these clusters is also very small compared to free CO. Magnetism calculations show that the magnetic moment of Agn Cr clusters decreases linearly from n = 6 to 12 and increases linearly from n = 12 to 16. The total magnetic moment of Agn Cr cluster is mainly localized on the Cr atom. The change of magnetic moment of Cr atom is related to the charge transfer between Cr and Ag atoms.

Tuning the magnetic properties of nonmagnetic monolayer Mo2C by doping and adsorption

For purpose of probing doping and adsorption induced ferromagnetism in nonmagnetic behavior of Mo2C monolayer, the electronic and magnetic properties of a transition metal atom (TM = V, Cr, Mn, Fe, Co, Ni) doped/adsorbed in/on Mo2C monolayer are researched by first principles methods. Firstly, both pristine and TM-doped/adsorbed in/on Mo2C monolayer show the metallic character. For Mn/Co-doped Mo2C monolayer, they present ferromagnetism with the total magnetic moments of 0.656 μB and 0.722 μB, which mainly come from the 3d electrons of Mn and Co sites. Moreover, the Cr/Mn/Fe/Co atom adsorption on Mo2C monolayer exhibit spin-polarized character. The exchange splitting in the d shell is discovered in Cr/Mn/Fe/Co-adsorbed onto monolayer Mo2C. Finally, the positive value of MAE for Co-doped and Cr/Mn/Co-adsorbed Mo2C systems indicates an out-of-plane easy axis, whereas the negative MAE value for Mn-doped Mo2C monolayer and Fe adsorption on Mo2C monolayer implies the easy axis in the surface.

Exploring the half-metallic ferromagnetism, dynamical and mechanical stability, optoelectronic and thermoelectric properties of K2NaMI6 (M = Mn, Co, Ni) for spintronic applications

The structural stability, optoelectronic and magnetic characteristics of K2NaMI6 (M = Mn, Co, and Ni) halide double perovskites have been demonstrated to be explained using density functional theory computations. The prominent generalized gradient approximation and integration of the mBJ potential are implemented to estimate the exchange–correlation potential, which is the only unidentified parameter in the state-of-the-art formulism. The structural optimization, mechanical stability criteria, and tolerance factor demonstrate the reliability of the double perovskites in a cubic structure with Fm3m symmetry. The elastic constants facilitated mechanical stability and revealed the brittle nature of these double perovskites. The spin-polarized electronic band profile and the behaviour of the dielectric constant and absorption coefficient in the spin-up and down channels show the presence of half-metallic nature in these materials. Additionally, we examined magnetism and the genesis of the half-metallic gap in this article. The half-metallic and magnetic properties are attributed to the unpaired electrons in the split d-orbitals of the M-sited elements in the crystal field. The Mn-, Co-, and Ni-based double perovskites were found to possess total magnetic moments of 4 μB, 4 μB, and 1 μB, respectively, with the transition metal atoms comprising up the majority of this magnetic moment. The Fermi level’s perfect spin polarisation promotes the potential application of double perovskites in spintronic technology.

First-principles calculations to investigate elastic properties, chemical bonds, electronic properties, magnetic properties, and phonon spectrum of CuNFe3 and CuNCo3

In this paper, the elastic properties, chemical bonds, electronic properties, magnetic properties, and phonon spectra of CuNFe3 and CuNCo3 synthesized in the experiment are calculated by first principles. The results show they are ferromagnetic metal compounds with covalent and ionic bonds. CuNFe3 and CuNCo3 have large bulk modulus B, Young's modulus Y, and shear modulus G, which are 191.01 GPa, 202.33 GPa, 159.65 GPa, 247.01 GPa, 58.67 GPa and 95.26 GPa, respectively, which indicates that they have compressive solid resistance. The total magnetic moment of CuNFe3 is 6.96 μB, and that of CuNCo3 is 4.17 μB, which suggests that they have broad application prospects in magnetic storage, computer core, magnetic recording materials and other fields.

Tunable electronic structure and magnetic characteristics of ZnO monolayer via vacancy defects, and domain/atomic doping

Two-dimensional ZnO monolayers have attracted great attention due to the potential applications in nano-optoelectronic and spintronic devices. However, tuning a sizeable band gap or magnetic properties is a significant challenge to the actual applications. Herein, the effects of monovacancy, divacancy, and voids defects, as well as domain/atomic doping on the electronic properties and magnetic characteristics of ZnO monolayer are investigated by spin-polarized density functional theory. The results demonstrate that single oxygen vacancy could realize the tunablity of bandgap and Zn vacancy could lead the transition between the nonmagnetic state and magnetic state. Remarkably, ZnO monolayers with different divacancies demonstrate magnetic or nonmagnetic characteristic. Zn divacancy produces the magnetic states due to the unpaired O atom, while O divacancy and Zn-O pair vacancy lead no spin polarization due to the occupied states. Void defects also can modify the magnetic properties of ZnO monolayer with the maximum magnetic moment of 1.258 μB. VI-IIA domain doping induces the nonmagnetic states, and widens or narrows the energy gap of ZnO monolayer. Additionally, ZnO monolayers with the doping of the selected atomic Rh and Ru exhibit the magnetic behavior with the total magnetic moment of 2.770 μB, and 3.678 μB, respectively. The total moments are mainly contributed by the dopants and their nearest O atoms. Our study demonstrates that the electronic properties and magnetic properties of ZnO monolayer could be effectively controlled by vacancy, divacancy, and voids as well as domain/atomic doping, being suitable for applications in optoelectronic and spintronic devices.

Tunable d0 magnetism of hexagonal boron nitride introduced through an adjacent doping strategy

To meet the current requirements of diluted magnetic semiconductors (DMSs) resulting from continuous advancements in spintronics, designing d0 DMSs with high stability, spin polarization, and Curie temperature is essential. Present research on introducing d0 magnetism is limited to monatomic doping, lacking regulation measures for local magnetic moments and long range magnetic coupling. Herein, an adjacent doping strategy is employed to introduce degrees of freedom for tuning the magnetic properties of d0 DMSs. It is observed that by introducing Si and O atoms as central and adjacent dopants, respectively, the intrinsically nonmagnetic hexagonal boron nitride (h-BN) exhibits significant local magnetic moments. Furthermore, it is observed that the ionization energy, total magnetic moment, magnetic coupling, and Curie temperature of the doped h-BN are susceptible to the Si–O coordination. Subsequently, a magnetic half-metal (Si–O3-doped h-BN) with high thermal stability, 100% spin polarization, long range ferromagnetic coupling, and high Curie temperature is designed through high Si–O coordination doping. This study proposes a feasible approach for introducing tunable d0 magnetism using the design of Si–O adjacent-doped h-BN as an example.

DFT insight into magnetoelectronic and optical properties of Mo-modified BaTiO3

Herein, the magnetoelectronic and optical characteristics of Ba1-xMoxTiO3 (x = 25%, 50%, and 75%) compound are computed by employing density functional theory (DFT). The robust half metallic ferromagnetic (HMF) character has been observed for Mo-incorporated BaTiO3. This behavior of Mo-modified BaTiO3 is due to the highly asymmetric behavior in both spin channels, semiconducting in dn-spin and metallic nature in up-spin version. The computed total magnetic moment (MTot) is found to be 4.0 μB for all substitutional concentrations which is mainly due to the Mo-4d states. In addition, the optical parameters (extinction coefficient, reflectivity, optical conductivity, refractive index, dielectric function, and absorption coefficient) are also calculated. The computed results suggest the suitability of studied material for spintronic and optoelectronic devices.

Insight into thermodynamic, optoelectronic, and magnetic characteristics of V doped BeSe

In present work, the magnetic and optoelectronic features of Be1-xVxSe (x = 6.25%, 12.5%, 18.75%, 25%) alloys are explored utilizing full potential linearized augmented plane wave (FP-LAPW) scheme based on spin dependent density functional theory (DFT). The analysis of spin-dependent electronic properties of V doped BeSe corroborated the half metallic ferromagnetism (HMF) at all V concentrations; spin-up version displays the metallic nature and spin dn channel represents the semiconductor character. The computed total magnetic moment (MTot) is found to be 3.00575, 3.00386, 3.00099 and 3.00023 μB at 6.25%, 12.5%, 18.75%, 25% doping concentrations, respectively, mainly arisen from V-3d state electrons ensured through spin magnetic density. Besides, dielectric function dependent optical properties (extinction coefficient, absorption coefficient, refractive-index, optical conductivity, and reflectivity) are also investigated within range of 0 ˗ 10 eV and obtained high absorption and low reflectance of the considered system in UV region. The overall analysis demonstrated studied material as a potential contender for utilization in spintronics and optoelectronics.

Long‐Range Magnetic Exchange Coupling in Quasi‐2D CrTe Ferromagnetic Thin Films

The 2D chromium telluride family (CrxTey) is an outstanding candidate for creating high‐density and dissipationless nanodevices because of its high Curie temperature, chiral spin patterns, and large saturation magnetic moment. However, the precise magnetic exchange mechanism and crucial phase transitional property of CrxTey must be fully analyzed. Herein, a large‐area CrTe (x:y = 1:1) single‐crystalline films deposited on an Al2O3 substrate. Based on the analysis of critical isothermal magnetization around the Curie temperature TC = 201 K and the modified Arrott plot, the precise critical exponents β = 0.386(3) and γ = 1.391(2) are obtained. Both their reliability and accuracy are also verified by Kouvel–Fisher theory, Widom scaling law, and scaling equation. Moreover, using the renormalization group theory, it is confirmed that CrTe belongs to a quasi‐2D Heisenberg‐like behavior with long‐range interactions. Finally, the density functional theory calculations indicate that, near the Fermi level, the CrTe band structure is mainly composed of Cr atom. The spin‐polarized density of states shows that the total magnetic moments are determined mainly by the polarized spin‐up t2g electron of Cr atom. This work is an important asset for a series of CrxTey materials in future spintronic applications.

Phase stability and physical property for off-stoichiometric Ni-Mn-Sb alloys including 4O phase

Large magnetic field-induced strains can only be found in modulated martensite for Ni-Mn-Sb alloys, but the theoretical research on this alloy which is generally concentrated in the austenite and non-modulated martensite (NM) ignores the modulated martensite. Therefore, in this paper, we systematically study the relationship between phase stability, physical property and composition in the full series Ni-Mn-Sb Heusler alloys (Ni24+xMn12-xSb12, Ni24+xMn12Sb12-x, Ni24-xMn12+xSb12, Ni24Mn12+xSb12-x) including four-layered orthorhombic modulated martensite (4O) by the first principles calculations. For phase stability, we determined that the critical components of 4O for Ni24+xMn12-xSb12, Ni24+xMn12Sb12-x and Ni24Mn12+xSb12-x is × = 6, x = 6 and × = 4, respectively. There is no 4O phase within the concentration range considered for Ni24-xMn12+xSb12. Moreover, the martensitic transformation sequences are also determined. As for physical properties, the transformation temperatures from austenite to 4O and NM phases are predicted respectively. Meanwhile, the ternary magnetic moment diagram of austenite, 4O and NM phases is constructed. The maximum value of total magnetic moment is distributed in the Ni-excess Sb-deficient system, while the minimum value of that is distributed in the Mn-excess Sb-deficient system. The origin of the above observations is explained by the competition between the Jahn-Teller effect in the electronic structure and the strength of the covalent bond. The results in this paper are expected to provide information for the composition design and performance optimization of Ni-Mn-Sb alloy.

Structures, Electronic, and Magnetic Properties of CoKn (n = 2-12) Clusters: A Particle Swarm Optimization Prediction Jointed with First-Principles Investigation.

Transition-metal-doped clusters have long been attracting great attention due to their unique geometries and interesting physical and/or chemical properties. In this paper, the geometries of the lowest- and lower-energy CoKn (n = 2-12) clusters have been screened out using particle swarm optimization and first principles relaxation. The results show that except for CoK2 the other CoKn (n = 3-12) clusters are all three-dimensional structures, and CoK7 is the transition structure from which the lowest energy structures are cobalt atom-centered cage-like structures. The stability, the electronic structures, and the magnetic properties of CoKn clusters (n = 2-12) clusters are further investigated using the first principles method. The results show that the medium-sized clusters whose geometries are cage-like structures are more stable than smaller-sized clusters. The electronic configuration of CoKn clusters could be described as 1S1P1D according to the spherical jellium model. The main components of petal-shaped D molecular orbitals are Co-d and K-s states or Co-d and Co-s states, and the main components of sphere-like S molecular orbitals or spindle-like P molecular orbitals are K-s states or Co-s states. Co atoms give the main contribution to the total magnetic moments, and K atoms can either enhance or attenuate the total magnetic moments. CoKn (n = 5-8) clusters have relatively large magnetic moments, which has a relation to the strong Co-K bond and the large amount of charge transfer. CoK4 could be a magnetic superatom with a large magnetic moment of 5 μB.

Giant magnetocaloric effects of MnNiSi-based high-entropy alloys near room temperature

The materials combining high-entropy alloys with good mechanical properties and magnetic materials with a significant magnetocaloric effect are among the best candidates for magnetic refrigeration. For this purpose, the high-entropy alloys (MnNiSi)1-x(FeCoGe)x (x = 0.4, 0.42, 0.45, and 0.47) were designed in this study. The effects of the Si/Ge ratio on the magnetocaloric effect and mechanical properties were also investigated. The results show that high-entropy alloy (MnNi)0.6Si0.62(FeCo)0.4Ge0.38 possesses a Vickers hardness value of 580.6HV2 and compressive strength of 267 MPa with respect to a significant entropy change of 48.5 J·kg−1K−1 under a magnetic field of 5 T near the Curie temperature of 308.8 K. In order to clearly understand the origin of this excellent comprehensive performance, the influence mechanism of crystal structure and configurational entropy were explored. Furthermore, the first-principles calculations indicated that the magnetic properties mainly originate from Mn atoms located in 3d sites and are influenced by the interaction between the Mn and Fe atoms. Additionally, the total magnetic moment and electron density are taken into account to reveal their influence on magnetocaloric properties.

Effect of Electron Correlations on the Electronic Structure and Magnetic Properties of the Full Heusler Alloy Mn2NiAl

In this theoretical study, we investigate the effect of electron correlations on the electronic structure and magnetic properties of the full Heusler alloy Mn2NiAl in the framework of first-principles calculations. We investigate the electron correlation effect as employed within hybrid functional (HSE) and also within the DFT+U method with varied values of parameters between 0.9 and 6 eV. The XA-crystal structure was investigated with antiferromagnetic orderings of the magnetic moments of the manganese. It was found that with a growth of the Coulomb interaction parameter, the manganese ions magnetic moment increases, and it reaches the value of 4.15–4.46 μB per Mn. In addition, the total magnetic moment decreases because of the AFM ordering of the Mn ions and a small magnetic moment of Ni. The calculated total magnetic value agrees well with recent experiments demonstrating a low value of magnetization. This experimental value is most closely reproduced for the moderate values of the Coulomb parameter, also calculated in constrained LDA, while previous DFT studies substantially overestimated this value. It is also worth noticing that for all values of the Coulomb interaction parameter, this compound remains metallic in its electronic structure in agreement with transport measurements.

Magnetocaloric effect and phase transformation of LaFe11.0M0.5Si1.5 (M = Cu, Ni, Mg) alloys

La (Fe,Si)13 is a promising magnetic refrigerant material. In this paper, the effects of Cu, Ni and Mg substitution of Fe on the magnetocaloric effect and phase transition properties of LaFe11.5Si1.5 alloys were studied by first-principles calculations combined with experiments. Through scanning electron microscopy–energy-dispersive spectroscopy analysis, it was concluded that after Cu partially replaced Fe, the content of the 1:13 main phase significantly decreased to 61.49%, and the contents of the α-Fe and LaFeSi phases increased. Cu was not conducive to the formation of the main phase. After Mg partially replaced Fe, the content of the 1:13 main phase increased to 99.12%, and Mg promoted the formation of the main phase. The electronic structure of the alloy was reconstructed by density functional theory (DFT), and the effects of the doping atoms on the magnetic properties of the alloys were studied. The calculation results showed that Ni atoms had the same weak magnetism as that in the magnetic moment vector direction of Fe atoms, Cu and Mg atoms had magnetism opposite to that in the magnetic moment vector direction of Fe atoms, and all alloys showed a lower total magnetic moment. According to the Arrott curve and the field dependence method of the magnetocaloric effect (MCE), when Cu = 0.5 and Ni = 0.5, the alloy phase transition changed from a first-order phase transition to a second-order phase transition, and when Mg = 0.5, the alloy still had a first-order phase transition.

Enhanced Magnetic Interaction between Ga and Fe in Two-Dimensional van der Waals Ferromagnetic Crystal Fe3GaTe2

Fe3GaTe2, a recently discovered van der Waals ferromagnetic crystal with the highest Curie temperature and strong perpendicular magnetic anisotropy among two-dimensional (2D) magnetic materials, has attracted significant attention and makes it a promising candidate for next-generation spintronic applications. Compared with Fe3GeTe2, which has the similar crystal structure, the mechanism of the enhanced ferromagnetic properties in Fe3GaTe2 is still unclear and needs to be investigated. Here, by using x-ray magnetic circular dichroism measurements, we find that both Ga and Te atoms contribute to the total magnetic moment of the system with antiferromagnetic coupling to Fe atoms. Our first-principles calculations reveal that Fe3GaTe2 has van Hove singularities at the Fermi level in nonmagnetic state, resulting in the magnetic instability of the system and susceptibility to magnetic phase transitions. In addition, the calculation results about the density of states in ferromagnetic states of two materials suggest that the exchange interaction between Fe atoms is strengthened by replacing Ge atoms with Ga atoms. These findings indicate the increase of both the itinerate and local moments in Fe3GaTe2 in view of Stoner and exchange interaction models, which results in the enhancement of the overall magnetism and a higher Curie temperature. Our work provides insight into the underlying mechanism of Fe3GaTe2's remarkable magnetic properties and has important implications for searching 2D materials with expected magnetic properties in the future.

Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe3Sn

We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easy-plane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K1≈−1.0×106 J/m3 at 300 K to −1.3×106 J/m3 at 2 K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 μB/f.u. and a magnetocrystalline anisotropy energy density of −0.57 meV/f.u. (−1.62×106J/m3) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of ∼3 T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness.

Slater-Pauling Behavior in Half-Metallic Heusler Compounds.

Heusler materials have become very popular over the last two decades due to the half-metallic properties of a large number of Heusler compounds. The latter are magnets that present a metallic behavior for the spin-up and a semiconducting behavior for the spin-down electronic band structure leading to a variety of spintronic applications, and Slater-Pauling rules have played a major role in the development of this research field. These rules have been derived using ab initio electronic structure calculations and directly connecting the electronic properties (existence of spin-down energy gap) to the magnetic properties (total spin magnetic moment). Their exact formulation depends on the half-metallic family under study and can be derived if the hybridization of the orbitals at various sites is taken into account. In this review, the origin and formulation of the Slater-Pauling rules for various families of Heusler compounds, derived during these two last decades, is presented.

First-principles calculations of the electronic, optical properties and quantum capacitance of Mn doped Sc2CO2 monolayer under biaxial strain

The electronic structures and quantum capacitance of Mn atom doped Sc2CO2 under biaxial strain are investigated by first-principles calculations. The results indicate that pristine Sc2CO2 monolayer is nonmagnetic, while Mn doping makes the system have the magnetic character, which is mainly from Mn and C atoms neighboring to Mn atom. The total magnetic moment under strain ranges from 2.16 μB to 2.69 μB. The local magnetic moment of Mn atom under strains ranges from 2.59 μB to 4.33 μB, and the variation in local magnetic moment has the largest value of 1.84 μB. Spin-up band structures under strain exhibit the characteristic of the indirect semiconductor, and have the largest band gap of 0.3 eV at −2 % strain. The spin-down band structures under strain show the character of direct semiconductor and the largest band gap is 1.83 eV at 2 % strain. Sc2CO2-Mn under strains except +5 % are suitable for cathode material, while Sc2CO2-Mn with +5 % strain changes to cathode material in ionic/organic system. Effective mass, work function, and optical properties are further explored.

Phosphorus, cobalt‐phosphorus, and nickel‐phosphorus clusters: Growth behavior, electronic, and magnetic properties

AbstractThe equilibrium geometries, and electronic and magnetic properties of phosphorus, cobalt‐phosphorus, and nickel‐phosphorus (Pn+1, CoPn, and NiPn, n = 1–24) clusters have been investigated by using first principle calculations. The doping with cobalt or nickel atom favors the endohedral structures in which the metal atom is encapsulated inside the phosphorus framework, while geometrical structures are metal‐dependent. The growth pattern behaviors and stabilities are examined from the binding energies, the second‐order energy differences, and the HOMO–LUMO gaps. The doping with Co or Ni atom contributes to strengthening the stability of the phosphorus frame with a marked improvement in the case of Ni atom. The total spin magnetic moment is enhanced with doping with Co atom. In contrast, the magnetic moment is quenched in the case of NiPn. Vertical electron affinities and ionization potentials are also reported and discussed.

First-principles calculations to investigate structural, electronic, magnetic, mechanical and thermodynamic properties of Half-Heusler alloy CoMnTe: Using GGA and GGA+U methods

In this paper, we study the structural, electronic, magnetic, mechanical and thermal properties of Half-Heusler CoMnTe, using the Density Functional Theory (DFT) with the generalized gradient approximation (GGA) and GGA plus the Hubbard correction (GGA+U). The obtained results show that the compound is more stable in γ-phase with the ferromagnetic (FM) configuration than the nonmagnetic (NM) among the three considered structural phases (α, β, γ) and there is no possibility of martensitic transformation under the tetragonal distortion effect. The computed total magnetic moments of CoMnTe by GGA and GGA+U are 4 μB and 4.13 μB, respectively, arising mainly from the Mn atom. The obtained density of states and band structures using GGA approach show that the compound exhibits half-metallic behavior with 100% spin polarization. As the Hubbard is added, the electronic properties show an electronic phase transition from half-metallic to metallic behavior with 68% spin polarization. While the thermal and mechanical properties show very small changes, confirming that the studied compound is mechanically and dynamically stable.