Total Magnetic Moment Research Articles

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.

Electronic and magnetic properties of SnC monolayer doped with 3d transition metals: A first-principles study

Unlike the conventional electronics, spin-based electronics (spintronics) uses electron spin as the information carriers. Therefore, it is required pure spin current for a high spintronic performance that can be generated employing materials with specific electromagnetic structures. In this work, the structural, electronic, and magnetic properties of SnC monolayer doped with 3d transition metals (TMs) are investigated by means of first-principles calculations. Results indicate that SnC monolayer is intrinsically non-magnetic two-dimensional material. Except Ti impurity, the substitutional incorporation of 3d TMs leads to the emergence of feature-rich electronic structures including magnetic semiconductor (in Sc-, V-, and Ni-doped systems) and half-metallic (in Cr-, Mn-, Fe-, Co-, Cu-, and Zn-doped systems) natures, which can be used to generate spin current by means of the spin filtering and spin injection approaches, respectively. Significant magnetism is also induced that is reflected in integer total magnetic moments between 1 and 4 μB. Herein, magnetic properties are produced mainly by host C atoms in the cases of Sc- and Zn-doped, meanwhile 3d TMs originate mainly the magnetism in the remaining cases with slight contribution from their first neighbor. Further, the magnetic anisotropy is also studied to determine the magnetization direction, while the existence of ferromagnetic (FM) and antiferromagnetic (AFM) ordering in ground state is also analyzed. Results may suggest the TMs-doped SnC monolayer as potential candidates for spintronic applications.

Magnetic and Electric Properties and Their Regulation of the Intrinsic Half‐Metallic Multiferroic Monolayers AV2S4

Abstract2D half‐metallic multiferroic materials have attracted great interest due to their rich novel performances and wide application prospect in nanoelectronics and nanodevices. Three intrinsic half‐metallic multiferroic monolayers AV2S4 (A = Na, K, and Rb) are predicted based on the first‐principles calculations. From the calculations, their ground states are all ferromagnetic and are completely spin‐polarized at the Fermi level. Their total magnetic moments are always 3.00 μB per primitive cell, which origin mainly from V‐ions. The two‐center electronic structure t2g6↑t2g4↓eg1↑ of V‐ions is proposed from the perspective of the crystal field theory to explain successfully the calculated magnetic moments. Interestingly, the alkali‐metal ions are non‐magnetic, but they may cause important influence on the magnetic coupling between transition ions, and then the half‐metallicity of these monolayers. Their electric and magnetic properties may be tuned by their charge states and strains. Especially, their half‐metallic stability may be evidently improved by the tensile strains. The half‐metallic gaps of these monolayers may be increased by about 67.4%, 50.8%, and 32.4% for NaV2S4, KV2S4, and RbV2S4 by the tensile strain 2.0%, respectively.

A Computational Understanding of Electronic, Magnetic, Mechanical, Thermoelectric, and Thermodynamic Properties of Rhodium‐Based Full‐Heusler Alloys Rh2MnX (X = Sc, Ti, Zr)

The present investigation has been carried to know the magnetic talent, mechanical strength, thermoelectric transport properties, and thermal results on Rh2MnX (X = Sc, Ti, Zr) full‐Heusler alloys. The structural investigation presents these alloys to be stable in 225 (Fm‐3m) cubic space group. Electronic results characterize these alloys as metallic in both spin channels. From elastic data results, these compounds are found to be mechanically stable in cubic space group. The mechanical study shows ductile nature for Rh2MnSc while it is brittle for Rh2MnTi and Rh2MnZr. The large value of bulk modulus for these compounds presents their stiffer resistance. The temperature‐dependent thermoelectric transport properties for these materials are calculated. The increasing nature of Ke/τ for all the three compounds presents their conducting nature. Increasing value of power factor with temperature advocates the use of these materials for high‐temperature thermoelectric devices. All the three materials present a large value of total magnetic moment greater than 4 μB and hence can contribute to advanced magnetic materials. The thermodynamic investigation is carried out using Gibbs2 program.

Study of Synthetic Antiferromagnetic Nanostructures Based on CoFeB/Ru/CoFe

A study of the magnetic properties of synthetic antiferromagnetic nanostructures (SAF) has been carried out. In the SAF structure, two ferromagnetic layers separated by a nonmagnetic metal are coupled by the exchange RKKY interaction (Ruderman— Kittel—Kasuya—Yoshida), which has an oscillating character. The total magnetic moment of the SAF structure is minimal with an antiparallel configuration of the magnetization of the ferromagnetic layers, due to which the effect on the magnetic layers in the structure is reduced. The structures under study have a number of unique properties and are used in the elements of nonvolatile magnetoresistive memory, in magnetic field transducers, and in spin logic devices. The characteristics of the SAF of CoFeB/Ru/CoFe nanostructures with the Ru layer thickness corresponding to the second antiferromagnetic maximum are obtained. The magnetization reversal curves of SAF structures with Ru thickness of 2.1 nm, 2.3 nm and 2.5 nm have been studied. The optimal ratio of ferromagnetic layers was selected to reduce the magnetic moment of the SAF structure. A study of the effect of thermomagnetic treatment on the properties of the SAF nanostructure was carried out, which showed that there are no significant changes in the magnetization reversal, and the magnetic saturation field slightly increases. The curves of magnetization reversal of CoFeB/Ru/CoFe structures fixed by the antiferromagnetic layer are presented. In addition, magnetization reversal curves of spin-tunnel magnetoresistive nanostructures with an antiferromagnetic layer and a SAF structure are presented, and an analysis of the thermal stability of the structures with SAF is also carried out.

First-principles calculations to investigate huge magneto-optic Kerr effect and thermoelectric properties of NdBiPt Heuslerene

Based on density functional theory, mechanical, electronic, optical, magneto-optic, and thermoelectric properties of the NdBiPt Heuslerene compound in three α, β, and γ phases were investigated. All phases have ground state points with equilibrium volume, and α phase has elastic stability with Young and Shear modulus of 80.913 GPa, and 24.834 GPa, respectively. Also, its total magnetic moment is 3 µB, which makes it as a half-metal. Along the x and y directions are semiconductor, and metallic behavior from optical view, with an optical gap in the infrared region. This compound has a surprising magnetic response to incident light, so its Kerr angle at 4 eV has a rightward rotation of 4.7ᵒ, and elliptical rotation angle has occurred at 4.5 eV. Thermoelectric studies showed significant Seebeck coefficient in all temperatures, and its positive sign, referred to the holes transporter. Also, its figure of merit coefficient reached 0.9 at low temperatures.

Magnetism caused by 3d-metals

Magnetic properties of Ag2S doped with 3d-transition metals were studied using density functional theory (DFT). It was found that magnetic elements such as Co, Cr and Mn cause magnetism in the structure. The nature of this magnetism is mainly from the 3d-states of the magnetic elements. The magnetic moment of supercells containing various concentrations (x= 2.08%, 4.1%, 8.3%) of dopant atoms has been studied. It was determined that the contribution of the magnetic elements is significant in the total magnetic moment of supercells. Calculation results reveal that when doped with impurity atoms, supercells show half metallicity and ferromagnetic (FM) nature which makes them the best candidate to be used in the field of spintronics.