Half-metallic Ferromagnetic Behavior Research Articles

Impact of Fe-doping on magneto-optoelectronic properties of beryllium sulfide (BeS): A first principles insight

The investigation of electronic, magnetic, structural, and optical properties of Be1-xFexS alloys is carried out by utilizing FP-LAPW method based on density functional theory (DFT) calculations. Fe-doped BeS exhibits half-metallic ferromagnetic behaviour at all doping concentrations, transforming it as favourable contender for spintronic devices. Our findings reveal the presence of 100 % spin polarization of electronic states. The calculated values of magnetic moments are 4.0, 8.0, and 16.0 μB for Be0.9375Fe0.0625S, Be0.875Fe0.125S and Be0.75Fe0.25S, respectively. The pristine BeS compound adopts a cubic close packing structure, known as the zinc blende structure, with the space group F-43m. The static values of R(0) are observed to be 0.21, 0.56, and 0.72 for Fe doped BeS at Be0.9375Fe0.0625S, Be00875Fe0.125S and Be0.75Fe0.25S, respectively. The maximum values of σ(ω) are computed as 16375.9 (1/Ω cm) for 6.25 %, 14336.5 (1/Ω cm) for 12.5 %, and 11002.1 (1/Ω cm) for 25 % Fe doped BeS. The present study unveils maximum optical absorption and conductivity in the ultraviolet (UV) region, suggesting its potential application in UV-based photovoltaic devices.

Cr and Mn doping AgNbO3 for high Curie temperature ferromagnetic half-metals

The alterations in the electronic and magnetic properties of AgNbO3 induced by Cr and Mn doping at two concentrations (6% and 14%) are investigated within the framework of density functional theory (DFT), both with and without the Hubbard correction (U) as well as HSE method. Half-metallic ferromagnetic behavior with 100% polarization is observed for all dopants. Double exchange coupling is the mechanism responsible for the ferromagnetic interaction in these materials. Our results also indicates that the correction with U-term and HSE method provide consistent values that closely align with experimental measurements, and significantly improve the standard DFT description. Finally, the value of the Curie temperature, which reaches 425.49 (K), exceeds the ambient temperature, revealing the potential use of this doped material for new spintronic devices.

Half metallic ferromagnetic and transport behavior of rare earth based CdGd2(S/Se)4 spinels

Spinel chalcogen compounds have garnered significant interest in recent ages because of their promising potential in optoelectronic and thermoelectric device applications. Here, we undertake an inclusive analysis of the structural, mechanical, electronic, magnetic, optical, and transport response of CdGd2(S/Se)4 utilizing WIEN2k code based on DFT. The determination of the crystal structure's ground state and the material's thermodynamic stability is investigated through energy vs. volume plots and ∆Hf calculation. Our analysis, including Poisson (v) and Pugh (B/G) ratios, reveals the ductile nature of the studied composition. Band gap assessments are conducted using the TB-mBJ approach, revealing the semiconducting nature of investigated compounds with direct band characteristics. Specifically, calculated band gap values are 2.2 for CdGd2S4 and 1.8 eV for CdGd2Se4. Additionally, analysis of optical properties and transport response underscores the perspective of these compositions for diverse optoelectronic and thermoelectric devices.

The electronic structures, half-metallic ferromagnetism, optical, and thermoelectric responses of the Co-doped Au2S chalcogenide compound

The structural, electronic, magnetic, optical, and thermoelectric properties of diluted magnetic semiconductors (DMS) based on the chalcogenide compounds Au3CoS2, Au2Co2S2, and AuCo3S2 have been investigated using all-electron first-principles calculations. We have used the GGA-PBEsol and the around mean-field (AMF) correction scheme (GGA-PBEsol + U) for the exchange-correlation energies. Firstly, we calculated the equilibrium ground state of properties. Afterward, we evaluated the magneto-electronic properties using the GGA-PBEsol and GGA-PBEsol + U approaches. The computed spin-polarized band structures and density of states revealed the half-metallic ferromagnetic behavior for the studied compounds from both approaches. The half-metallicity is mainly due to the p-d hybridization of S and Co atoms. We also estimated the Curie temperatures using the mean-field approximation, and the results exceeded the ambient temperature. The real and imaginary components of the dielectric function, as well as the refractive index and reflectivity, were calculated up to 13.0 eV for both spin directions to explore the optical responses of AuCo3S2, Au2Co2S2, and Au3CoS2 compounds. The thermoelectric responses have also been reported for the spin-up orientation using the semi-classical Boltzmann transport theory and indicate that the half-metallic behavior is maintained at high temperatures. Finally, both the importance and potential applications of the studied compounds are discussed in this study.

DFT+U, TB-mBJ, and hybrid approaches: investigating electronic topology and magnetic properties in Sn-doped Co2TiGa

Cobalt-based Heusler compounds represent a new class of Heusler alloys which absorbed a lot of attention due to their performance in spintronics and magnetic devices. in this paper we have studied and analyzed the electronic structure and half-metallic ferromagnetic properties of Co2TiGa and Sn substituted at Ga site via the density functional theory (DFT) based first principle calculations with GGA-PBE, PBE+U, TB-MBJ exchange correlation potential and HSE06 approach. The band structure topology indicates that the parent ternary Heusler compound is ferromagnetic half-metallic with a half-metallic gap (band gap in the minority channel). The gap is increased according to the correction made on the exchange correlation potential. The half-metallic ferromagnetic behavior is confirmed by the total magnetizations which are very close to integrals Bohr magneton (1 μ B and 3μ B for Co2TiGa and Mn2TiGa0.5Sn0.5, respectively). The origin of half-metallic ferromagnetic is the p − d exchange and double-exchange interaction between the Co d-t2g states and neighboring Ti atom. The substitution effect on half-metallicity for Co2TiGa0.5 Sn0.5 was investigated in the tetragonal structure. The spontaneous magnetization obeyed the Slater-Pauling rule, indicating the Co2TiGa0.5 Sn0.5 is half-metal with 100% spin polarization.

Exploring multiferroicity, half-metallic phase, and curie temperature in X = B/C/N/F-Doped KNbO3: a DFT aspect

Multiferroic materials provide an astonishing platform for next-generation spintronic devices such as magnetoresistive random access memory. Herein, ferroelectric, electronic, and magnetic properties of the pristine and X = B/C/N/F-doped KNbO3 (KNO) perovskite oxides are explored using ab initio calculations along with modified Becke-Johnson potential, where X is doped at O-site (X@O) in both KO- and NbO2-layers. Our calculations revealed that the pristine motif is a non-magnetic insulator having an energy band gap (E g ) of 2.80 eV and spontaneous polarization (P) of 41 μCcm−2, which are close to the experimentally observed values of 3.34 eV and 37 μCcm−2, respectively. The computed enthalpy of formation and elastic parameters confirm the thermodynamic and mechanical strength of the doped configurations, respectively. It is established that X-dopants significantly reduce structural distortions and have negative influence on the value of P. The most distinctive feature of the current work is that the B/N-doped KNO system for X@O in the KO-layer exhibits n-type half-metallic (HM) ferromagnetic (FM) behavior with an E g of 1.46/2.96 eV which is sufficiently large enough to prevent any magnetic transition. In contrast, C and F-doped structures are FM insulator and n-type non-magnetic metallic, respectively. Along with this, X = B/C/N-doped KNO system for X@O in the NbO2-layer displayed FM insulating nature, while the F-doped motif becomes an n-type non-magnetic metallic. The total magnetic moment for the B/N-doped structure is 1.0, which also hints the HM FM behavior. Finally, the estimated Curie temperature using the Heisenberg 2D Hamiltonian model in magnetic doped structures is found to be high enough to be used for practical purposes.

First-principles simulations of magnetic properties of Co- and Ni-doped ZnSe

We purposed to analyze the theoretical ab initio study of ferromagnetism and to estimate Curie temperature of Co2+ and Ni2+ 3d transition metal (TM) ions doped Zn1-x TM x Se compounds for 12.5 % and 6.25 % concentrations of impurity TM(Co, Ni) atoms. The calculations are carried out using the norm-conserving Fritz-Haber-Institute ionic pseudopotentials based on density functional theory within the local spin density approximation and Hubbard U (U(Znd)=4.5 eV; U(Sep)=3.8 eV) corrections. The analysis of the total and partial electron density of states shows the half-metallic ferromagnetic behavior with a half-metallic bandgap. The theoretically obtained total magnetic moments of TM(Co, Ni) doped Zn1-x TM x Se systems are equal to 3 μB and 4 μB, correspondingly.

Thermodynamic, mechanical stability, and magneto-electronic features of Ti2-based quaternary Heusler alloys Ti2CoGa1−xCux (x=0, 0.25, 0.5, 0.75, and 1): A DFT investigation

In this work, we have used the full-potential linearized augmented plane wave (FP-LAPW) method implemented in the WIEN2k code combined with the generalized gradient approximation (GGA) of the density functional theory (DFT) to study the structural, elastic, mechanical, electronic, magnetic, and thermodynamic properties of the parent ternary inverse Heusler compounds based on Titanium and Cobalt Ti2CoGa, Ti2CoCu in the Hg2CuTi-type structure and their quaternary alloys Ti2CoGa[Formula: see text]Cux ([Formula: see text], 0.5, 0.75) for the chosen concentrations using a supercell with 16 atoms. We have calculated the structural properties, such as the lattice parameters, bulk modulus, and its first derivative, which are in good agreement with those that have been obtained based on other published theoretical methods. Also, we calculated the elastic constants of the studied Heusler alloys, and we found that these materials are elastically stable, ductile, and anisotropic. Therefore, the electronic and magnetic properties indicate that Ti2CoGa exhibits a half-metallic (HM) ferromagnetic behavior, while Ti2CoCu shows a metal and a non-magnetic (NM) character. Their quaternary alloys are found to be nearly HM ferromagnetic materials, with a magnetic moment mainly due to the atom Ti. Furthermore, the quasi-harmonic Debye model, which incorporates the lattice vibrations, was used to estimate the thermodynamic effects on some macroproperties of the Ti2CoGa[Formula: see text]Cux alloys. Successful results were achieved for the variations of the primitive cell volume, bulk modulus, heat capacities, and Debye temperature with pressure and temperature, respectively, in the ranges of 0–30[Formula: see text]GPa and 0–1400[Formula: see text]K. To our knowledge, no analogous investigations on the mechanical and thermodynamic properties of the Ti2CoGa[Formula: see text]Cux ([Formula: see text], 0.5 and 0.75) alloys have been performed to date. As a result, it is predicted that Ti2CoGa[Formula: see text]Cux Heusler alloys will be promising candidates for actual applications in spintronic devices.

DFT insights on the Be1-xCrxS alloys for optoelectronic and magnetic devices

In this work, the electro-optical and magnetic characteristics of Be1-xCrxS (x= 6.25%, 12.5% and 25%) are brought into investigation by employing full potential linearized augmented plane wave (FP-LAPW) scheme designed within density functional theory (DFT). The stability of the Be1-xCrxS alloy is justified by the negative values of formation energy. The band structures and density of states are examined by using GGA functional. Be1-xCrxS compound demonstrates the half-metallic (HM) ferromagnetic behavior for all doping concentrations; spin-up channel reveals the metallic character and other spin version displays the semiconductor (SC) behavior. The values of total magnetic moment (µB) are recorded as 4.0 8.0 and 16.0 µB for corresponding 6.25%, 12.5% and 25%, which mainly arises owing to Cr-3d state. Moreover, optical features including dielectric function ε(ꞷ), reflectivity, refraction, and absorption are explored within range of 0-10 eV. The maximum absorption of incident photons was found in ultraviolet (UV) span which implies their importance for optoelectronic applications. Results reveal that the studied alloy has potential applications in magnetic and optoelectronic gadgets.

Ground state structural, electronic and magnetic properties of Mg-doped LaMnO[formula omitted] perovskite: GGA+U study

The effect of Mg doping on the ground state structural, electronic and magnetic properties has been investigated by means of GGA+U calculations. The inspection of the structure, magnetic moment data and density plots, show that by substituting La by Mg at the La site at a concentration of 0.25, the compound exhibits a Pbnm orthorhombic structure and a half metallic ferromagnetic behaviour with degenerated Mn-eg states. The corresponding average A-site cation radius 〈rA〉 value does not allow metallic-insulator phase transition in the compound. However, by doping Mg on Mn site with the same proportion, the resulting compound shows a Pbnm orthorhombic structure and a half metallic behaviour with degeneracy lifting in Mn-eg states. Our results obtained for LaMn0.75Mg0.25MnO3 agree more with experimental data than those obtained for La0.75Mg0.25MnO3, suggesting that Mg will prefer to substitute at the Mn site due to their close ionic radii.

Ti, V, Cr, Mn, Co, and Ni substitution effect on structural, electronic, thermodynamic and magnetic properties of MgS and MgSe for spintronics

For the purposes of fitting the characteristics of the Magnesium sulfide (MgS) and, Magnesium selenide (MgSe) semiconductors in Spintronic applications, a theoretical ab-initio investigation of Transition metals (TM=Ti, V, Cr, Mn, Co, Ni) substitution is performed. The equilibrium properties have been studied in the zinc-blende phase of MgS and MgSe. The effects of temperature and pressure on the structural, electronic, thermodynamic, and magnetic properties of our systems are explored as well. It is found that the introduction of the TMs in MgS and MgSe brings out a half-metallic ferromagnetic behavior with 100% polarization around Fermi level in Ti, V, Cr, Co and Ni cases, contrary to the Mn case where the half-metallic feature does not appear. The double exchange mechanism was the mechanism responsible for magnetism in these systems. Finally, the high Curie Temperate (Tc) of the ferromagnetic systems reveals that Ti, Cr and V substitutions could play a significant role in spintronic applications.

Effect of 3d transition metal impurities doping on electronic and magnetic properties of CeO2

The effect of transition metal (TM) impurities, namely Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, on the electronic and magnetic properties of Ceria dioxide is studied using the Korringa-Kohn-Rostoker method combined with the coherent potential approximation (KKR-CPA). Calculations indicate that pure CeO2 is a nonmagnetic indirect semiconductor. Doping this compound with transition metals results in three main groups based on their electromagnetic behavior. The first group involves CeO2 doped with Sc, Ti and Zn which show a lack of magnetism at low concentrations. The second group of TMs, including V, Mn, Fe and Ni, induces half-metallic character and ferromagnetic behavior. Finally, when Cr, Co and Cu are substituted in CeO2, this doping creates magnetic semiconductors with a direct band gap. The origin of the magnetic states is further discussed and the Curie temperatures are determined. The present work shows that controlling impurity type and concentration renders Cerium dioxide a potential candidate for spintronic applications.

Electronic, Structural, Optical, and Magnetic Characteristics A2MgS4 of (A=Dy, Er) Spinel Sulfides: A Density Functional Theory Study

Density functional theory (DFT) simulations are performed to explore the physical features of Dy2MgS4 and Er2MgS4. Local density approximation with Hubbard potential (LDA + U) functional is utilized to examine the magnetic and electronic features. Half metallic ferromagnetic (HMF) behavior is confirmed by the spin‐resolved density of states (DOS) and band structure (BS) plots. Spin‐resolved BS and DOS show that Dy2MgS4 and Er2MgS4 for spin‐down are metallic, whereas both compounds in spin‐up show semiconductor nature with the bandgaps of 1.731 and 3.081 eV for Dy2MgS4 and Er2MgS4, correspondingly. Both compounds also feature exchange energies and crystal field splitting, indicating the magnetic characteristics. The estimated magnetic moments of X2MgS4 (X = Dy, Er) are 20μB and 12μB, correspondingly, also revealed by spin‐polarized magnetic density. Optical properties such as refractive index n(ω), absorption coefficient α(ω), dielectric constant , reflectivity R(, extinction coefficient k(ω), and optical conductivity σ(ω) are also explored. The optical bandgaps for MgX2S4 (X = Dy, Er) are 1.70 and 1.51 eV, respectively; it shows that both are transparent to visible light. Results indicate that both materials can be suitable for spintronic and solar‐cell usage.

Magnetic, optical, electronic, structural and thermoelectric features of A2MgS4 (A=Sm, Tb): A DFT study

The spinel A2MgS4 (A = Sm,Tb) sulfides were analyzed by first-principle using the WIEN2k software based on density functional theory (DFT). Dynamic stability has been adequately explained using enthalpy of formation values (ΔHf) (−3.50 for Sm2MgS4 and -3.57 eV for Tb2MgS4). By examining band structure (BS) with spin polarized density of states (DOS), it is confirmed that Sm2MgS4 exhibits half-metallic ferromagnetic (HMF) behavior whereas Tb2MgS4 has semiconducting nature with a bandgap (Eg) of 1.56 in spin (↑) up and 0.94 eV in spin (↓) down channel. The estimated magnetic moments (μB) of sulfo-spinel Sm2MgS4 and Tb2MgS4 are 19.99931 and 24 μB, respectively. Transport properties such as thermal (k/τ) and electrical (σ/τ) conductivities, Power factor (PF), Seebeck coefficient (S), and figure of merit (ZT) are computed to determine the thermal behaviour of both spinels. From thermoelectric (TE) analysis, Tb2MgS4 maximum value of figure of merit (ZT) is 0.731 at 800 K, whereas the maximum S is 234 for Sm2MgS4 at 500 K and 267 μV/K for Tb2MgS4 at 350 K, hence, Tb2MgS4 is more efficient TE material than Sm2MgS4. Additionally, optical characteristics including absorption coefficient α(ω), extinction coefficient k(ω), dielectric constants ε(ω), reflectivity R(ω), refractive index n(ω), and optical conductivity σ(ω) are investigated. Computational results show that A2MgS4 (A = Sm, Tb) materials are potential candidates for spintronics, optoelectronics, and TE devices.

Investigations of the structural, electronic, magnetic, and optical properties of RbSrX (X = C, Si or Ge) by density functional theory

The electronic, structural, magnetic, and optical properties of RbSrX (X = C, Si or Ge) are performed by using the full-potential linearized augmented plane wave (FP-LAPW) method and generalized gradient approximation (GGA) within Density functional theory (DFT). The electronic band structures and Density of states show metallic nature for electrons spin-down, while for spin-up, these compounds have a gap of 2.01, 1.95, and 1.50 eV, respectively, which show a half-metallic ferromagnetic behavior in the magnetic moment of 1μβ. The structural parameters show that the band gap decreases as we move from up to down in the IV-A group. The s, p, and d states have been controlled by electronic properties for RbSrX (X = C, Si or Ge). Optical parameters, such as reflectivity, dielectric function, optical conductivity, absorption coefficient, loss function, and refractive index, have also been calculated and presented.

Electronic, Thermodynamic Stability, and Band Alignment Behavior of the CoVSi/NaCl Heterojunction

We report the band discontinuity of the CoVSi/NaCl heterointerface. First principle calculations based on density functional theory using GGA, GGA + U, and GGA + mbJ approximations were applied to study the structural, electronic, and band alignment properties. Structural and thermodynamic stability studies indicate that this semiconductor - dielectric heterojunction can be synthesized experimentally in thermodynamic equilibrium conditions. The valence and conduction band offset values (VBO and CBO) were 0.74 and 3.02 eV, respectively. Also, the effective electron affinity parameter (χ e) for both CoVSi and NaCl were calculated as ∼1.51 and ∼0.769 eV, respectively, using Anderson’s law. The study of the electronic structure expresses the occurrence of half-metallic ferromagnetic behavior with a narrow band gap of about 0.09 eV. In this heterojunction, electrons and holes were confined to the CoVSi layers, and conduction band minimum and valence band minimum were replaced in the CoVSi layers. This restriction, applied to load carriers on one side of the interface, significantly increases the light-material interaction in light-emission programs. Therefore, this heterojunction can be recommended for light-emitting applications and thin atomic layer materials with quantum confinement of charge carriers.

Electronic, optical and magnetic characteristics of V doped BeS

Electronic, magnetic and optical features of V doped BeS compound are obtained with FP-LAW technique. A comparative investigation is performed among electronic band structure (BS), total and partial density of states (PDOS) is presented with 6.25, 12.5, 18.75 and 25% concentration of V. The results of electronic BS and density of states (DOS) show half metallic ferromagnetic (HMF) behavior with direct band gap (Eg). The calculated Eg are 2.8, 2.9, 3.3 and 3.7 for Be0.9375V0.0625S, Be00875V0.125S, Be0.8125V0.1875S and Be0.75V0.25S, respectively. For the optical feedback of TM doped BeS material, the imaginary and real part of dielectric function has been studied with the absorption coefficient, extinction coefficient, reflectivity, optical conductivity, and refractive index up to 15 eV. It is noted that with the increment of Eg, the static dielectric constant increases. Furthermore, the magnetic characteristics of resultant compound are examined. The HMF nature of TM doped BeS in electronic and magnetic properties may makes resultant compounds a potential candidate for optical and spintronic appliances.

Transport Properties of Novel LaCoTiIn Equiatomic Quaternary Heusler Alloy for Thermoelectric Energy Conversion

The emergence of new thermoelectric materials for energy generation is crucial to satisfying the world's energy demand. The electron charge density and thermoelectric transport properties of the LaCoTiIn quaternary Heusler alloy were investigated in this study. We used the Generalized Gradient Approximation (GGA – PBE) exchange correlation potential to illustrate the physical properties of a material. The electronic structure of the alloy shows half-metallic ferromagnetic behavior. The minority spin channel's small band gap enhances its thermoelectric characteristics. The high electrical conductivity, small thermal conductivity, and good figure of merit all indicate that this material could be a suitable material to employ in thermoelectric energy conversion.

The effect of Sn doping on the structural, electronic and magnetic properties of rutile CrO2: A DFT approach

The effect of Sn doping on the structural, electronic and magnetic properties of rutile CrO2 has been extensively investigated in this study. Sn doping induces distortions in the CrO6 octahedra due to variations in <Cr–O–Cr angles and Cr–Cr distances, respectively in the rectangular four chain columns (RFCCs) and the double chains. The half-metallic ferromagnetic behaviour of CrO2 is preserved at 50% doping of Sn for Cr. Nevertheless, the electronic and magnetic properties of the doped material Cr0.5Sn0.5O2 change significantly under the influence of Coulomb interaction U. The correlation between itinerant Cr-dyz/xz electrons is triggered when U is applied. As a result of spin polarization, the valence/conduction bands shift towards/away from the Fermi level (EF), resulting in a reduction in semi-conducting spin gaps. At U = 6 eV, this material eventually encounters a metal-insulator transition (MIT), retaining its ferromagnetism. The Cr-dxy state and the bonding components of dyz/xz states become occupied and move much below the EF, whilst the anti-bonding components of dyz/xz states become unoccupied and move well above the EF. As a result, a band gap of Eg∼0.2 eV is opened in near the EF. The ferromagnetism of insulating Cr0.5Sn0.5O2 is due to strong p-d hybridizations between the occupied Cr 3d and O 2p states. More interestingly, the ferromagnetic Curie temperature (Tc) increases about 44–59 K due to Sn doping in CrO2.

The effect of vacancies on the magnetic and optical properties of monolayer alpha lead oxide (α-PbO): A density functional theory study

In this study, we analyzed the effect of vacancies on the structural, electronic, magnetic, and optical properties of monolayer α-PbO using density functional theory (DFT). We found that the most significant atomic displacements occurred in the direction away from the Pb vacancy site in the monolayer α-Pb0.94O system. Bandgaps of 2.424 ​eV and 1.144 ​eV were obtained for monolayer α-PbO and α-PbO0.94 systems, respectively. The monolayer α-PbO and α-PbO0.94 systems also exhibited non-magnetic properties. However, monolayer α-Pb0.94O showed half-metallic ferromagnetic behavior with a total magnetic moment of 1.56 ​μB per cell, which was promoted by the dangling bonds of O atoms around the vacancy site. Monolayer α-Pb0.94O also had a more plasmonic state and optical dichroism than the monolayer α-PbO and α-PbO0.94 systems. These results indicate the essential properties of monolayer α-PbO with Pb vacancies for potential nonlinear plasmonic device applications.