Stable Magnetic Phase Research Articles

Effect of Ti doping on phase stability and half-metallicity of the Co2FeGe compound: GGA and mBJ-GGA approaches

Density Functional Theory (DFT) calculations were performed using the full-potential linearized augmented plane wave (FP-LAPW) method to study the effect of Ti doping on Co2FeGe systems. The both GGA and mBJ-GGA formalisms were employed in this study. For both the L21 and XA structures, ferromagnetic, ferrimagnetic and paramagnetic phases were considered, and lattice optimization was conducted to determine the most stable magnetic phase. The Co2FeGe and Ti2FeGe Heusler alloys were found to be stable in the ferromagnetic state with the L21 structure. In contrast, the XA-type ordering was observed for the CoTiFeGe alloy. The density of states and band structure calculations for the CoTiFeGe (XA structure) alloy revealed half-metallic behavior, which is notable for its potential in achieving high spin polarization. Additionally, half-metallic character was observed for the Co2FeGe alloy with L21-type ordering when using the mBJ-GGA formalism. The calculated elastic constants confirmed that these systems satisfy the mechanical stability criteria. Furthermore, the systems with x = 0.00 (Co2FeGe) and x = 1.00 (Ti2FeGe) comply with the Slater-Pauling rule for half-metallicity in alloys, given by Mtot = NV-24. According to the mBJ-GGA method, the total magnetic moments of Co2FeGe and CoTiFeGe are 6 μB and 1 μB, respectively. Meanwhile, the Ti2FeGe compound follows the condition Mtot = NV-18 and has a total magnetic moment of approximately 2 μB. The optoelectronic properties were examined through analysis of the optical constants, confirming semiconducting behavior for both x = 0.00 and x = 1.00.

Structural stability, electronic, magnetic, thermoelectric, optical and thermodynamic properties of CoTiFeGe and Co2Fe0.25Mn0.75-xTixGe alloys

Density Functional Theory (DFT) calculations are performed using full potential linearized augmented plane wave (FP-LAPW) method to study CoTiFeGe and Co2Fe0.25Mn0.75-xTixGe (x = 0, 0.25, 0.50, 0.75) systems through GGA and mBJ-GGA formalisms. The lattice equilibrium optimization was conducted to determine the stable magnetic phase state of these systems. It was found that the systems exhibit stability in a ferromagnetic nature, with the exception of the Co2Fe0.25Mn0.75Ge compound, which displays ferrimagnetic behavior. Electronic band structures and density of states for our systems show a half-metallic character using mBJ-GGA, except the Co2Fe0.25Mn0.75Ge system, which exhibits metallic behavior. Furthermore, the studied systems adhere to the Slater-Pauling rule condition for half-metallicity of alloys Mtot = ZV-24. Optoelectronic properties have been analyzed using optical parameters, confirming semiconducting behavior. Optical reflections with minimal loss and the existence absorption are observed in the infrared and visible areas suggest that the studied systems are suitable for optoelectronic devices. Additionally, a comprehensive assessment of the thermodynamic properties of the systems was carried out to investigate their thermodynamical stability against temperature and pressure change. The transport properties of these systems were systematically investigated, revealing that our alloys present the poor thermoelectric matter.

Semiconducting Characteristic of Antiferromagnetic Al4X3Mn (X = P, As and Sb) Compounds with Ab Initio Simulation Methods

This research reports the electronic characteristics of ternary aluminium-based Al4X3Mn (X=P, As and Sb) compounds for the most stable magnetic order which is A-type antiferromagnetic. The related systems are comforming 215 space number with P-43m space group which is simple cubic crystal structure. The computations in this research have been done within the framework of Density Functional Theory. The calculations utilized Perdew-Burke-Ernzerhof type correlation functionals within the meta-generalized gradient approximation. For considered four different type magnetic orders, the visualized volume-energy plots and the calculated formation energy values imply that the magnetic nature of these compositions is A-type antiferromagnetic. Besides, the investigated electronic natures in the detected stable magnetic phase of these systems are semiconductor since the band gaps were observed in their electronic band structures and density of states (Eg = 0.36 eV for Al4P3Mn, Eg = 0.33 eV for Al4As3Mn, and Eg = 0.18 eV for Al4Sb3Mn).

First-Principles Calculations to Investigate Spin-Oriented Magnetic Phases, Band Gaps, Elastic, and Thermodynamic Calculations of VNi2O4

In this study, spin and U-Coulomb interactions-dependent electronic structure, pressure-dependent elastic, and thermodynamics studies of VNi2O4 were performed. The ferromagnetic (FM) phase was the most stable magnetic phase. The lattice parameter was calculated as 8.32 Å. The bulk modules were calculated as 197.695 GPa and 198.038 GPa, respectively, in the initial condition and the elastic calculations, so the initial and elastic conditions were compatible. VNi2O4 material had band gaps of 1.597 eV, 2.159 eV, 2.659 eV, 3.094 eV, 3.439 eV, 3.729 eV, and 3.978 eV in the majority spin electrons in the Generalized Gradient Approximation (GGA), and U-Coulomb interactions (U = 1, 2, 3, 4, 5 and 6 eV), respectively. Hence, it was a true half-metallic ferromagnetic. VNi2O4 was ductile at 0 GPa, with a Debye temperature of 586.596 K. The net magnetic moment of VNi2O4 was 6.00 µB/f.u. As a result, VNi2O4 provides all the necessary conditions for spintronic applications.

Impact of structural distortion on electronic and magnetic properties of La[formula omitted]MnVO[formula omitted] double perovskite: An ab initio approach

We have studied the detailed structural, electronic, and magnetic properties of La2MnVO6 double perovskite considering both ab initio and semiempirical parameters within the density functional formalism. We have also considered the strong electron correlation (density functional theory plus the Hubbard potential U) in our calculations to determine the ground state of the compound. Investigation of detailed structural properties with both ab initio and semiempirical parameters reveals that the structure obtained with the semiempirical parameters is more distorted, having more distorted octahedra than the theoretically optimized structure obtained with the variable-cell relaxation method. The stable magnetic phase of the compound is obtained as ferromagnetic with use of the energy minimization principle with the Hubbard potential. Study of the electronic properties shows that the compound is a half-metal with the ab initio parameters, whereas it behaves as a semimetal with the semiempirical parameters. The final ground state of the compound is concluded to be a ferromagnetic metal.

A first-principles study of stabilities, magnetic, electronic, elastic and transport properties of the metal borides TM2B (TM = Mn, Fe, Co and Ni)

This work addresses the physical properties of the highly correlated electron systems; transition metal borides TM2B (TM = Mn, Fe, Co and Ni) and provides a solid foundation for resolving the longstanding debate concerning the stable magnetic phase of Mn2B. The generalized gradient approximation along with Hubbard U (GGA + U) approach handling the high correlated electron systems; a valuable insight into this article has been utilized in the domain of Density Functional Theory. The calculated lattice parameters are found consistent with the experiments. The optimization energies in different magnetic phases and magnetic susceptibilities reveal that Mn2B is antiferromagnetic (AFM) in nature. The replacement of the TM in these intermetallics; transform the AFM behavior of Mn2B in to ferromagnetic (Fe2B and Co2B) and then paramagnetic (Ni2B), respectively. Electronic properties, electrical resistivities and thermal electronic conductivities of these compounds confirm their metallic nature. The investigated elastic properties demonstrate the stability and show that Fe2B is harder and brittle among this series while the rest compounds are ductile. All these intermetallics are incompressible and possess high melting temperatures. Based on the above properties, it is expected that these compounds could be used in high temperature technology like furnaces, reactors, aerospace and other high temperature processing equipments.

Effect of Hubbard U on the electronic and magnetic properties of Ca[formula omitted]VMoO[formula omitted] double perovskite

In this work, we have studied the detailed electronic and magnetic properties of Ca2VMoO6 double perovskite using the density functional theory (DFT). We have also considered the Hubbard potential (DFT+U) in our calculations and studied its effect on the electronic and magnetic properties of the compound. The electronic properties, that is, the density of states and band structures reveal that the compound is a half-metal. The reason for the metallic behavior of the compound is due to the competitive interaction between crystal field splitting and exchange splitting in the Mo d-states. The different possible magnetic phases of the compound are discussed and using the minimum energy principle with GGA and GGA+U formalism, the stable magnetic phase of the compound is found to be ferromagnetic.

Prediction of van Hove singularities, excellent thermoelectric performance, and non-trivial topology in monolayer rhenium dichalcogenides

Two-dimensional (2D) thermoelectric materials are gaining more intense attention with the ever-increasing global demand for energy. Recently, the search for compounds exhibiting excellent thermoelectric and topological characteristics has also attracted research exploration. In this study, a systematic investigation of Re-based transition metal dichalcogenides (TMDs) (ReX 2 , X = S, Se, and Te) through first-principles calculations identified the stability and electronic properties of the 1T dp (1 T double prime), 1 T’, 1 T, and 2H phases for the pristine bulk and monolayer ReX 2 . Formation energy and phonon dispersion calculations showed that the bulk and monolayer structures are only stable in the 1T dp structure. The calculated bandgaps of bulk under the hybrid functional approach are 1.567 eV, 1.429 eV, and 0.745 eV, while those of the monolayer phases are 1.902 eV, 1.658 eV, and 1.323 eV for ReS 2 , ReSe 2 , and ReTe 2 , respectively. Moreover, van Hove singularities (vHss) are observed in monolayer ReX 2 suggesting possible superconductivity. Remarkably, the calculated figure of merits (ZT) of bulk and monolayer ReX 2 with values up to 2.30 presents them as excellent materials for thermoelectric (TE) applications since good TE materials have ZT > 0.4. In addition, the effect of one- (1 h) and two-sided (2 h) hydrogenation on the structural, electronic, magnetic, and topological properties of monolayer ReX 2 were also investigated. Two-sided hydrogenation caused a stable structural phase transition from 1 T dp to 1T. A ferromagnetic phase transition was also observed upon the two-sided hydrogenation of ReS 2 (2h-ReS 2 ) and the one - sided hydrogenation of ReSe 2 (1h-ReSe 2 ). Finally, one-sided hydrogenation of monolayer ReSe 2 and ReTe 2 (1h-ReSe 2 and 1h-ReTe 2 ) resulted in non-trivial topological phases as confirmed by the calculated Z 2 and Chern topological invariant numbers. Our findings show that the 2D Re-based TMDs exhibit highly tunable properties which have the potential for thermoelectric and spintronics applications. • Monolayer ReX2 is thermodynamically stable in the distorted 1 T phase (1Tdp) • van Hove singularities are present in monolayer ReX2 suggesting superconductivity • Excellent thermoelectric properties are observed in bulk and monolayer ReX2 • Stable structural and magnetic phase transition occurred upon hydrogenation of ReX2 • Hydrogenation of monolayer ReX2 induced non-trivial topological phases

Phase Transitions in Magneto-Electric Hexaferrites.

Hexaferrites have long been the object of extensive studies because of their great possibility for applications-permanent magnets, high-density recording media, microwave devices, in biomedicine, to name but a few. Lately, many researchers' efforts have been focused on the existence of the magneto-electric effect in some hexaferrite systems and the appealing possibility of them being used as single-phase multiferroic and magneto-electric materials. As indicated by theoretical analyses, the origin of the large magneto-electric effect can be sought in the strong interaction between the magnetization and the electric polarization that coexist in insulators with noncollinear magnetic structures. The hexaferrites' magnetic structure and, particularly, the specific magnetic spin ordering are the key factors in observing magneto-electric phases in hexaferrites. Some of these phases are metastable, which hampers their direct practical use. However, as the hexaferrites' phase diagrams reveal, chemical doping can be used to prepare a number of noncollinear stable magnetic phases. Since the magneto-electric effect has to do with the magnetic moments ordering, it seems only logical that one should study the cation substitutions' influence on the magnetic phase transition temperature. In this paper, we summarize recent examples of advances in the exploration of magnetic phase transitions in Y-type hexaferrites. In particular, the effect is emphasized by substituting in Y-type hexaferrites the nonmagnetic Me2+ cations with magnetic ones and of the magnetic Fe3+ cations with nonmagnetic ones on their magnetic properties and magnetic phase transitions. The work deals with the structural properties of and the magnetic phase transitions in a specific Y-type hexaferrite, namely, Ba(Sr)2Me2Fe12O22.

First-principles study of polar magnets corundum double-oxides Mn2FeMO6 (M = W and Mo)

The physical properties of the corundum double-oxides Mn2FeMO6 (M = W and Mo) are investigated using density functional theory (DFT). The structure relaxation in different spin orders are performed and ferrimagnetic is found the most stable magnetic phase. The compounds are dielectric materials with band gap values 1.84 and 2.03 eV. These materials are polar magnets because of the coexistence of contradictory properties such as polarization and magnetization, which are observed very rarely. The electric polarization arises due structure distortion and cation orbital configuration of M atom, while the magnetization occurs due to unpaired dn of Mn and Fe orbital configuration. The compounds understudy are suitable for ferroelectric and magneto-electric applications due to their large spontaneous polarization (58.16 and 69.24 µC/cm2) and magnetic moments (3 and 3.43 µB/f.u). These multiferroic Mn2FeMO6 exhibit a profound interplay between electrical polarization and the applied magnetic field. The calculated values of piezoelectric coefficient, d33 = 264 and 606 pC/N are comparable to lead-based piezoelectric materials. A set of mechanical parameters revealed that Mn2FeMO6 are mechanically stable in rhombohedral phase. The applied strain has great influence on the physical properties of these two compounds.

A comprehensive investigation of structural and magnetic phase stability, electronic, magnetic and thermoelectric properties of Co2FeZ (Z = Al, Ga, Si, Ge, S, Se and Te) Full Heusler alloys

A series of full Heusler (FH) alloys Co2FeZ (Z = Al, Ga, Si, Ge, S, Se and Te) have been investigated using density functional theory (DFT) with full potential-linearized augmented plane wave (FPLAPW) method within generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) functional. Most stable structures are determined by considering four different atomic arrangements i.e. L21-I/II (conventional) and XA-I/II (inverse) configurations. Stable magnetic phases like anti-ferromagnetic (AFM), nonmagnetic (NM) and ferromagnetic (FM) are evaluated and results revealed that FM phase is the most stable of all alloys. Spin band structures are calculated by applying GGA and GGA + mBJ approach. The results showed the half metallic nature of Co2FeAl and Co2FeGe alloys. The obtained band diagrams are compared with density of states (DOS) and revealed that the both Fe and Co atoms contributes maximum in total magnetic moment (MM). The calculated values of total magnetic moment (MT) of all compounds range from 4 to 6 μB and are in well agreement with the findings of Slater-Pauling Rule (SPR). Both alloys i.e. Co2FeAl and Co2FeGe showed 100% level of spin polarization (SP) at Fermi level. Mean field approximation (MFA) is employed to determine Curie temperature (Tc) and the values thus obtained are higher than room temperature. Furthermore, the thermoelectric parameters i.e. Seebeck coefficient (S) along with thermal (κ) and electrical (σ) conductivities for both Co2FeAl and Co2FeGe alloys are calculated and discussed in detail. The obtained results envisaged that the investigated alloys are suitable candidates for thermoelectric and spintronic applications.

Role of External Stimuli in Engineering Magnetic Phases and Real-Time Spin Dynamics of Co/Mn Oxides.

Magnetism in atomically thin two-dimensional (2D) materials can be easily manipulated by alloying, functionalization, external ultrafast laser pulse, strain, electric field, etc. In this work, we have performed a series of spin-resolved density functional theory calculations on 2D magnetic hexagonal transition-metal oxide alloys, CoMnO4. We have explored different alloy patterns and found the most stable magnetic phases in each pattern, resulting in a stable ferromagnetic (FM) ground state depending upon the pattern. We have used Janus functionalization in these materials to tune the magnetic nature of the system from FM to antiferromagnetic (AFM) states. To further control the spin dynamics, we have applied an ultrafast laser pulse to the Janus systems to explore an AFM-to-FM transition process. Finally, applying strain and electric field to the Janus alloys allows us to tune the structure-property relationship in the 2D layers to obtain desirable spin arrangements.

Magnetic behavior and Curie temperature of Dy doped MgSe: Ab-initio calculations

In this paper, we have studied the structural, electronic and magnetic properties of Magnesium selenide (MgSe) doped with a rare earth magnetic impurity “Dy” in the zinc blende structure (Mg1−xDyxSe). The ab-initio calculations are performed using the Akai-KKR code, based on the density functional theory. The host compound is a nonmagnetic semiconductor with a gap energy of 1.45 eV. Doping with only 6% of Dy gives MgSe a metallic behavior with a spin polarization of 83% at the Fermi level. In addition, the ferromagnetism is the most stable magnetic phase in the doped system. The Dy impurity contributes with various magnetic moments ranging from 0.23 muB to 0.31 muB for concentrations of 6% and 20% respectively. Besides, Vegard's law is used in order to evaluate the variation of the lattice parameter as a function of Dy concentration. Lastly, the Curie temperature is also calculated, it turns out to be equal to 260 K, which is lower than the room temperature. Doped MgSe is an excellent choice for electronic devices owing to its metallic characteristic below the Tc temperature.

Ab-initio Investigation of Structural, Optoelectronic, and Magnetic Properties of SmAlO3

The cubic perovskites have attained great importance in magneto-electronic storage devices due to their electromagnetic nature and because of their direct band-gap. The cubic perovskites’ structural, electronic, optical, and magnetic characteristics were investigated using Density Functional Theory (DFT), using Wein2k-code with the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method. In Kohn-sham equations, the Generalized Gradient Approximation (GGA) has been used as an exchange-correlation function. Investigated structural properties by analytical methods as well as DFT establish to be similar in comparison with the results of experimental data. The optimizations of the stable magnetic phase authenticate the low-temperature experimental observations. The optical spectra also deliver various linear optical parameters. So the current investigation signifies a valuable approach to analyze the comprehensive data about structural, magneto-electronic, and optical properties that can create a prospect to comprehend profuse physical occurrences of SmAlO3. In addition to it, authorize material scientists to implement the material for valuable applications.

A Theoretical Study on Electronic Behavior and Mechanical Properties of Ferromagnetic Manganese Selenide: AgMn2Se4

In this study, the electronic behavior and mechanical properties of the ferromagnetic chalcospinel manganese-based selenide (AgMn2Se4) which crystallized in face centered cubic structure with space group Fd3 ̅m and space number 227, were investigated. All ab initio calculations were carried out by Generalized Gradient Approximation (GGA) under spin polarization. For this composition, three different type magnetic orders were considered to detect the most stable magnetic character. For the given composition, the results of the computations indicate its ferromagnetic nature since this compound has a lower ground state energy in this magnetic order than in other magnetic phases. After determining the most energetically stable magnetic phase, the electronic behavior in this magnetic arrangement was examined. The observed electronic band structure under spin polarization of this compound shows that this selenide system is almost half-metallic material due to having small band gap (Eg = 0.09 eV) in the minority spin state. In addition, the mechanical stability was determined with the help of elastic constants which were also employed to determine the mechanical characteristics of this compound.

The effect of the composition and pressure on the phase stability and electronic, magnetic, and elastic properties of M2AX (M = Mn, Fe; A = Al, Ga, Si, Ge; X = C, N) phases.

The magnetic properties of M2AX (M = Mn, Fe; A = Al, Ga, Si, Ge; X = C, N) phases were studied within DFT-GGA. The magnetic electronic ground state is determined. The investigation of the phase stability of M2AX phases is performed by comparing the total energy of MAX phases to that of the set of competitive phases for calculation of the phase formation enthalpy. As the result of such an approach, we have found one stable compound (Mn2GaC), and seven metastable ones. It is shown that several metastable MAX phases (Mn2AlC, Fe2GaC, Mn2GeC, and Mn2GeN) become stable at a small applied pressure (1.5-7 GPa). The mechanical, electronic and elastic properties of metastable MAX phases are studied.

Magnetic compensation phenomena and paramagnetic behavior on coronene -Like Superlattice: A Monte Carlo study

The magnetic properties of Coronene -Like Superlattice (CLS) have been investigated via Monte Carlo study. The system has been described by Hamiltonian contain the (S–S), (σ-σ), (σ-S) spins, external magnetic and the crystal field applied on the two spins S and σ. The several more stable magnetic phases of CLS are obtained under effect of crystal field, exchange interactions and magnetic field. The critical and compensation temperatures of CLS are found for a several exchange interactions between the spins (S–S, σ-S) and crystal fields for a fixed value of exchange interactions between spins σ-σ. Magnetic hysteresis cycles of CLS are obtained for a several temperatures, exchanges interactions (S–S), (σ-σ) and crystal filed Dσ. In particular, the results show that the effect of: temperature, exchange coupling, magnetic field and crystallized field, play an important role in the presence of the more saturated magnetic phases and their effect on the magnetic hysteresis cycle.

The investigation of electronic nature and mechanical properties under spin effects for new half-metallic ferromagnetic chalcogenides Ag3CrX4 (X = S, Se, and Te)

This study presents the electronic and mechanical characteristics of ternary silver-based Ag3CrX4 (X = S, Se, and Te) chalcogenides having simple cubic crystalline structure (SC), conforming P4-3m (space group: 215) that are studied under the spin-polarized Generalized Gradient Approach (GGA) within the framework of the Density Functional Theory (DFT). The stable magnetic phase has been determined as the ferromagnetic (FM) phase for all studied systems. Then, phase stability, mechanical, thermal and electronic characteristics of Ag3CrX4 chalcogenides have been reported. In the calculated spin polarized electronic band structures for Ag3CrX4 chalcogenides, as an indicator of half-metallic behavior, metallicity has been observed in the majority spin channel, while indirect band gaps (1.04 eV for Ag3CrS4, 1.10 eV for Ag3CrSe4, and 1.25 eV for Ag3CrTe4) have been determined in the minority spin channel. Moreover, Ag3CrX4 chalcogenides have been found as thermodynamically stable and structurally synthesizable considering the calculated negative formation enthalpies. Elastic constants of studied chalcogenides satisfying Born-Huang criteria's pointed out the mechanical stability of materials. The predicted mechanical properties determined with elastic constants revealed that Ag3CrX4 chalcogenides belong to soft and ductile material family.

Electronic structure and magnetic properties of the Mg-rich intermetallic NdNiMg5 by hybrid density functional theory

Mg-rich intermetallic NdNiMg5 in orthorhombic phase with space group Cmcm (No. 63) has been studied theoretically using hybrid functional (HF–B3PW91) within the frame work of density functional theory (DFT). The calculated structural parameters and geometries are found in good agreement with the experiments. The electronic properties of the material reveal the metallic nature. Nd 4f-states splitting show that A2, y[t1] and z[t1] contributed in the valence band; x[t1], ksi[t2] and eta[t2] in conduction band; where zeta[t1] state completely lay at the Fermi level make the compound metallic. The electrical properties show that the material has significant conductivity above the room temperature. The stable magnetic phase of the compound is optimized which show that the material is stable in G-type antiferromagnetic (AFM) phase and Nd–Ni direct magnetic exchange interactions are involved. The calculated effective magnetic moments of Nd is 3.70 μB per unit cell. The post-DFT calculations also confirm the AFM phase of the compound with Neel temperature (TN) = 25 K and Curie-Weiss constant (θ) = −23 K. Based on the above physical properties it is expected that this intermetallic could be used in spin valve and magnetic memory devices.

The investigation of electronic, anisotropic elastic and lattice dynamical properties of MAB phase nanolaminated ternary borides: M2AlB2 (M=Mn, Fe and Co) under spin effects

Abstract In the present study, the structural, electronic, magnetic, anisotropic elastic and lattice dynamic properties of the ternary metal borides M 2 A l B 2 ( M = M n , F e and C o ) known as MAB phases have been investigated by density functional theory. The obtained results from the structural optimizations show that all these compounds have negative formation enthalpy implying the thermodynamic stability and synthesizability. The spin effects on the M 2 A l B 2 phases have been studied with the plotted energy-volume curves for different magnetic phases (antiferromagnetic (AFM), ferromagnetic (FM), and paramagnetic (PM)) of these compounds. The stable magnetic phase for the M n 2 A l B 2 compound is found to be AFM while the magnetic nature of F e 2 A l B 2 and C o 2 A l B 2 compounds are FM. The calculated electronic band structures with the total and orbital projected partial density of electronic states imply that these ternary metal borides have metallic behavior. Also, the mentioned compounds have mechanical and dynamic stability due to the calculated elastic constants and the observed phonon dispersion curves. Some thermodynamic properties have been investigated by means of phonon dispersion curves. Furthermore, the anisotropic elastic properties have been visualized in three dimensions (3D) for Young’s modulus, linear compressibility, shear modulus, Poisson’s ratio, and sound wave velocities.