Slater-Pauling Rule Research Articles

Structural, elastic, electronic, and magnetic properties of Si-doped Co2MnGe full-Heusler type compounds

The structural, electronic, magnetic and elastic properties of Co2MnGe1-xSix (x = 0, 0.25, 0.50, 0.75, and 1) compounds are investigated by first-principles calculations within the generalized gradient approximation (GGA). The calculated structural parameters of these compounds show a slightly decreasing lattice constants and similarly decreasing lattice volumes and enthalpies of formation on increasing Si substitution x. The band structure calculations estimate that these compounds at their optimized lattice constants are half-metallic ferromagnets. The calculated total magnetic moment values are all integers, which is typical for half-metallic materials with a half-metallic bandgap (EHM) in the minority states. Besides, the total magnetic moments of these compounds are fully compatible with the Slater-Pauling rule showing the half-metallicity and large spin polarization desired for spintronics applications. The partial substitution of the Ge atom by the Si does not affect the atomic magnetic moment and total magnetic moment. The obtained values of structural parameters, total and atomic magnetic moments for x = 0 and 1 stoichiometric compounds are in good agreement with experimental and theoretical results. The elastic constants are studied for all compositions of x in order to verify the mechanical stability of these compounds. Born’s stability criterion implemented on elastic constants of Co2MnGe1-xSix (x = 0, 0.25, 0.50, 0.75, and 1) compounds confirm that these materials are mechanically stable. Other elastic parameters like bulk modulus (B), shear modulus (G), ratio of B/G, Young’s modulus (E), Poisson’s ratio (ν), and Shear anisotropic factor (A), which are the significant elastic moduli for technological applications have been thoroughly investigated. Consequently, these compounds, especially Co2MnGe1-xSix (x = 0.25, 0.50, 0.75) mixed systems, are promising candidates for practical applications in the field of spin electronics.

Competition of L21 and XA ordering in Fe2CoAl Heusler alloy: a first-principles study

The physical properties of Fe2CoAl (FCA) Heusler alloy are systematically investigated using the first-principles calculations within generalized gradient approximation (GGA) and GGA+U. The influence of atomic ordering with respect to the Wyckoff sites on the phase stability, magnetism and half metallicity in both the conventional L21 and XA phases of FCA is focused in this study. Various possible hypothetical structures viz., L21, XA-I, and XA-II are prepared by altering atomic occupancies at their Wyckoff sites. At first, we have determined the stable phase of FCA considering various non-magnetic (or paramagnetic), ferromagnetic (FM) and antiferromagnetic (AFM) configurations. Out of these, the ferromagnetic (FM) XA-I structure is found to be energetically most stable. The total magnetic moments per cell are not in agreement with the Slater-Pauling (SP) rule in any phases; therefore, the half-metallicity is not observed in any configurations. However, FM ordered XA-I type FCA shows 78% spin polarization at EF. Interestingly, the results of XA-I type FCA are closely matched with the experimental results.

First-principles search for half-metallic ferromagnetism in CsCrZ2 (Z = O, S, Se or Te) Heusler alloys

Exploring highly spin-polarized materials is crucial for the development of spin-based devices. In this paper, we investigate the atomic structure, electronic, half-metallic and magnetic properties of the CsCrZ2 (Z = O, S, Se or Te) Heusler alloys, by performing first-principles calculations based on density functional theory (DFT). The geometry optimization process shows that the alloys are more stable in Cu2MnAl type structure than in Hg2CuTi one. To find a magnetic ground state, the total energy of the alloys is calculated in the non-magnetic (NM), ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering. We find that, the FM ordering yields the lowest energy, thereby confirming that the alloys are FM in the ground state. On computing the cohesive and formation energy in the ground state, it is found that alloys are chemically and thermodynamically stable, respectively. Spin polarized band structures and density of states (DOS) demonstrate that the CsCrO2, CsCrS2 and CsCrSe2 alloys are true half-metals with 100% spin-polarization at the Fermi level, while the CsCrTe2 alloy is predicted as highly spin polarized material. Furthermore, the CsCrO2, CsCrS2 and CsCrSe2 alloys possess 2.529, 2.250 and 2.050 eV gaps in the spin down band structure, respectively. The calculated total magnetic moments reveal that half-metallic alloys have an integral total magnetic moment of 3.000 μB, which satisfies the Slater-Pauling rule Mt = Zt-16. The main contribution to the total magnetic moment comes from the Cr atoms (about 3.9 μB). Furthermore, the Curie temperature TC calculated within classical Heisenberg model is estimated to be about 822 K (CsCrO2), 685 K (CsCrS2), 753 K (CsCrSe2) and 636 K (CsCrTe2). The obtained high spin polarization and above room temperature FM ordering make the materials as promising materials to be used in spintronic technology.

Complete spin gapless semiconductivity in equiatomic quarternary Heusler material TiZrMnAl

A new equiatomic quarternary Heusler compound TiZrMnAl has been theoretically predicted. Two possible structural configurations are considered under the site preference rule and their equilibrium lattices have been derived. Electronic band structures identify TiZrMnAl compound as the spin gapless semiconductors in both two structure types. The total magnetic moments of TiZrMnAl are both equal to zero with the partial moments of Ti and Zr antiparallelly aligned to that of Mn. This integral value of total moment follows the Slater-Pauling rule in the form of Mt = Zt − 18, where Mt represents the total magnetic moment and Zt is the total number of valence electrons. The mechanical and dynamic stabilities of TiZrMnAl have also been validated and strong elastic anisotropy is further revealed with the calculated directional dependent Young’s modulus and shear modulus for both structures. Besides, the effect of random swap disorder between Ti and Zr atoms has been examined and it is found that through the whole swap range, TiZrMnAl maintains its fully compensated spin gapless semiconductivity, which is a very good property for possible applications in spintronic devices. Lastly, the uniform and tetragonal strains have been accessed and their effects on the electronic and magnetic properties have been studied. This systematic study can provide a comprehensive reference for the further development of Ti and Zr based quarternay Heusler compounds and even inspire other relative studies for the exploration of new spin gapless semiconductors.

Computational discovery of the novel half-metallic full-Heusler alloys Mn2LiAs and Mn2LiSb

The structural, elastic, electronic and magnetic properties of the novel full-Heusler alloys Mn2LiAs and Mn2LiSb are determined to explore their structural stability and half-metallicity. The method used is the first-principles method based on density functional theory. Calculations show that the Hg2CuTi-type structure is more energetically favourable than the conventional Cu2MnAl-type structure and is thermodynamically and mechanically stable for both alloys. The Hg2CuTi-type Mn2LiAs and Mn2LiAs alloys are half-metallic ferrimagnets and have a total magnetic moment of 2.000 μB per formula unit. They follow the Slater-Pauling rule and have an indirect energy gap in the spin-down channels with values of 1.176 and 1.269 eV at equilibrium lattice constants of 5.793 and 6.132 Å, respectively. The half-metallicity is kept within the limits of a wide lattice constant range. The spin polarisation ratio is 100% and the total magnetic moment is 2.000 μB. Mn2LiAs and Mn2LiSb alloys, which can be synthesised via experiments, are promising candidates for spintronic applications.

Investigations on Gilbert damping, Curie temperatures and thermoelectric properties in CoFeCrZ quaternary Heusler alloys

Exchange interactions and Curie temperatures of CoFeCrZ (Z=P, As, Sb, Ge) quaternary Heusler alloys are studied by using the spin-polarized relativistic Korringa-Kohn-Rostoker method. Electronic calculations show that the CoFeCrZ alloys apart from CoFeCrP are ferromagnetic half-metals, and their integer magnetic moments obey the Slater-Pauling rule. It is confirmed that the calculated Curie temperatures are evidently higher than room temperature. Further, we discuss the dependency of magnetic moments and Curie temperatures with respect to lattice constants. A smaller Gilbert damping parameters imply that these alloys have lower energy loss in spintronics applications. In addition, the thermoelectric properties of CoFeCrZ in both spin channels are calculated based on the BoltzTrap code. Results indicate that the Seebeck coefficients of CoFeCrZ (Z=As, Sb, Ge) are remarkably higher than 1000 μV/K. Overall, we think that the CoFeCrAs, CoFeCrSb and CoFeCrGe alloys are promising candidates in future spintronic and thermoelectric applications.

Examining the half-metallicity and thermoelectric properties of new equiatomic quaternary Heusler compound CoVRhGe under pressure

Structural, electronic, magnetic and thermoelectric properties of a new equiatomic quaternary Heusler (EQH) compound CoVRhGe are studied using the full-potential linearized augmented plane-wave (FP-LAPW) approach and Boltzmann transport theory. The structural optimization is carried out by considering different configurations of atomic positions at non-magnetic and ferromagnetic states. Obtained results show that the considered compound is half-metallic with a spin-down semiconducting band gap of 0.812 eV and its magnetic properties do follow the Slater-Pauling rule. CoVRhGe quaternary has high Seebeck coefficient in the spin-down (spin-dn) state and high electrical conductivity in the spin-up state resulting from the semiconductor and metallic nature, respectively. Finally, the pressure effect on the electronic, magnetic and thermoelectric properties of the studied material is also systematically examined.

Theoretical study of the structural, electronic and magnetic properties of equiatomic quaternary CoTcCrZ (Z = Si, Ge, P) Heusler alloys

In this study, full potential linearized augmented plane wave (FP-LAPW) method has been used to calculate structural, electronic and magnetic characteristics of CoTcCrZ (Z = Si, Ge, P) Equiatomic Quaternary Heusler alloys (EQHAs). Furthermore, Generalized Gradient Approximation (GGA) and Hubbard potential (GGA+U) are adopted in the parametrization of Perdew-Burke-Ernzerhof (PBE). Structural stability calculations confirmed that the Type II is the most stable structure of all considered alloys. Further investigations were carried out for the most stable Type (i.e. Type II). Comparison of electronic structure calculations performed by GGA and GGA+U methods concluded that considered alloys show half-metallic nature for GGA+U method. Magnetic moments for all these alloys are determined which are found in accordance to the Slater-Pauling rule. Half-metallicity has been verified in all these considered Heusler alloys (HAs) from the calculations of spin-polarization at the Fermi level (EF). Moreover, the Curie temperature (Tc) is estimated by employing mean field approximation (MFA).

Pressure dependent half-metallic ferromagnetism in inverse Heusler alloy Fe2CoAl: a DFT+U calculations.

We report the electronic and magnetic properties along with the Curie temperature (TC) of the inverse full Heusler alloy (HA) Fe2CoAl obtained by using the first-principles computational method. Our calculations suggests that Fe2CoAl is a magnetic metal when treated within PBE-GGA under the applied compressive pressures. However, the implementation of electron–electron (U) (i.e., GGA+U) with varying compressive pressure (P) drastically changes the profile of the electronic structure. The application of GGA+U along with pressure induces ferromagnetic half-metallicity with an integer value of total magnetic moment ∼4.0 μB per unit cell. The integer value is in accordance with the Slater–Pauling's rule. Here, we demonstrate the variation of semiconducting gap in the spin down channel. The band gap increases from 0.0 eV to 0.72 eV when increasing the pressure from 0 to 30 GPa. Beyond 30 GPa, the electronic band gap decreases, and it is completely diminished at 60 GPa, exhibiting metallic behaviour. The analysis of the computed results shows that the treatment of electron–electron interactions within GGA+U and the application of compressive pressure in Fe2CoAl enables d–d orbital hybridization giving rise to a half-metal ferromagnet. The TC calculated from mean field approximation (MFA) decreases up to 30 GPa and then increases linearly up to 60 GPa.

Ductile and metallic nature of Co2VZ (Z= Pb, Si, Sn) Heusler compounds: A First Principles Study

Herein, optoelectronic, elastic and magnetic properties of L21 structured Co2VZ (Z= Pb, Si, Sn) full Heusler compounds have been investigated by two methods. One is full potential linearized augmented plane wave (FP-LAPW) method as implemented in WIEN2k and second is pseudo potential method as implemented in Atomistic Tool Kit-Virtual NanoLab (ATK-VNL). All these compounds shows zero band gap in majority spin channel in the both simulation codes and a finite band gap are 0.33 and 0.54 eV in Co2VZ (Z= Pb, Sn) alloys (semiconducting) respectively. Due to minority-spin channel near the Fermi level as implemented in WIEN2k code and showing 100% spin polarization except Co2VSi (metallic) with zero band gap. These compounds found to be perfectly half-metallic ferromagnetic (HMF). However, above mentioned compounds shows finite band gaps in ATK-VNL code. The calculated magnetic moment of these compounds Co2VZ (Z= Pb, Si, Sn) are 3.00 and 3.00, 3.02 and 2.96, 3.00 and 3.00µB in WIEN2k and ATK-VNL codes respectively. Thus we have observed that the calculated vales by these simulation codes and Slater-Pauling rule have nice tuning. Optical properties of these compounds like as reflectivity, refractive index, excitation coefficient, absorption coefficient, optical conductivity and electron energy loss have been analyzed. Absorption coefficient and electron energy - loss function values are increases as we increase the value of energy. The vales of Pugh’s ratio B/G is greater than 1.75 for all compounds and showing ductile nature with positive value of Cauchy pressure (CP = C12 – C44) and shows metallic behavior of Co2VZ (Z= Pb, Si, Sn) compounds.

Calculation of magnetic moment of inverse-Heusler alloy Fe2CuAl via first-principles-based tight-binding model

Heusler alloys have been known since the 19th century and have fascinated researchers because of their wide range of applications, especially related to their magnetic properties. The magnetic moment of a few of these materials can be predicted by simply counting their valance electrons [this is called the Slater-Pauling (SP) rule]. However, this simple counting rule does not work in many other cases. Inverse-Heusler alloys are a sub-class of Heusler alloys, and in many cases also do not follow the SP rule. Fe2CuAl (FCA) is an inverse-Heusler alloy for which the SP rule predicts a magnetic moment of 2.00 μB. However, experimental results give a magnetic moment of 3.30 μB. Motivated by this discrepancy, we study this material theoretically to gain a microscopic understanding of how the magnetic moment forms. For this purpose, we construct a first-principles-based tight-binding model incorporating an on-site Hubbard repulsion U between each d orbital and a Hund coupling J between different d orbitals of a given atom in the system. We use the Green’s function technique and apply the mean-field approximation to solve the model. The results show the magnetic moment of FCA depends on U and J. We find that the magnetic moment given by the SP rule (2.00 μB) corresponds to a plateau in our magnetic moment vs J curves for various values of U, and that the experimental magnetic moment (3.30 μB) corresponds to a point on the curves rising above the plateau.

FIRST-PRINCIPLES STUDY OF MAGNETISM AND HALF-METALLIC PROPERTIES OF THE D0 QUATERNARY HEUSLER ALLOYS BANYO (Y = K, RB AND CS)

First-principles theory was applied to investigate the electronic, elastic, magnetic, and half-metallic behaviors of the newly designed quaternary Heusler compounds BaNYO (Y = K, Rb and Cs) without 3d transition metal elements. However, elastic properties show that our compounds are ductile and anisotropic. The calculated results show that our compounds are half-metallic with an integer magnetic moment of 2.00 µB at the equilibrium lattice parameter, with 100 % spin polarization around the Fermi level, which follows the famous Slater-Pauling rule, Mtot =16 − Zt, Mtot is the total magnetic moment and Zt is the total number of valence electrons. Based on its equilibrium and strained lattice constants, the magnetic and half-metallic behaviors of this compound have been discussed in detail. Large half-metallic gaps of BaNYO (Y = K, Rb and Cs) compounds of 0.95, 0.90 and 0.85 eV, respectively have been found in our work, which is nearly larger than any previous study. Furthermore, the calculated negative formation energy and cohesive energy indicate that these two alloys have good chemical stability. This theoretical investigation provides further insight into the application of BaNYO compounds as spintronic materials.

Theoretical Studies of the Structural, Electronic and Magnetic Properties of the CoFeCeZ (Z = P, As and Sb) Quaternary Heusler Alloys

In this paper, we investigate the structural, electronic and magnetic properties of CoFeCrZ ([Formula: see text], As,Sb) quaternary Heusler alloy, using the first-principles full potential linear muffin-tin orbital (FP-LMTO) method within the spin gradient generalized approximation (GGA) for the exchange and correlation potential. Our results demonstrate that in ferromagnetic phase, the all alloys CoFeCrZ are stable in type-1 configuration and are half-metallic ferromagnets (HMF) with gaps of 0.99[Formula: see text]eV, 0.57[Formula: see text]eV and 0.70[Formula: see text]Ev, respectively. The obtained negative formation energy shows that CoFeCrZ alloys have strong structural stability. The calculated total magnetic moment, [Formula: see text] for all alloys exhibit Slater-Pauling rule, [Formula: see text]. At zero pressure, the three alloys shown 100% spin-polarization at Fermi–level [Formula: see text] with high Curie temperatures [Formula: see text]. Our calculation indicate also that the half-metallicity and high magnetic moment of CoFeCrP, CoFeCrAs and CoFeCrSb are robust against the lattice compression (up to 7.80%, 5.40% and 11%, respectively). On the basis of these results, it is suggested that the CoFeCrZ Heusler could be suitable for spintronics devices applications.

Phase stability and magnetic properties in Co2Cr(Al,Si) shape memory alloys

The phase stability and magnetic properties of the parent phase in the Co2Cr(Al,Si) shape memory alloys were systematically investigated. For the Co-rich portion in the vicinity of stoichiometric composition, the phase boundaries of B2 phase in equilibrium with Co solid solution (A1) phase at 1473 K were identified and the compositions showing martensitic transformation were also determined within the B2 single-phase region. The addition of Si greatly expands the B2 single-phase region compared with that of the Co-Cr-Al ternary system. The Curie temperature and spontaneous magnetization of the L21 phase, which is formed by the order-disorder transition from the B2 phase during water quenching from 1473 K, were 345–540 K and 2.1–2.6 μB/f.u., respectively. The values of spontaneous magnetization were lower than those expected from the Generalized Slater-Pauling rule and the ab-initio calculation.

Ab-initio calculations of the structural, mechanical, electronic, magnetic and thermoelectric properties of Zr2RhX (X= Ga, In) Heusler alloys

We investigate the ground state properties namely structural, mechanical, electronic and magnetic properties and thermoelectric behavior of the inverse Heusler alloys Zr2RhGa and Zr2RhIn. Ab-initio calculations are carried out through the WIEN2k package. Both Zr2RhGa and Zr2RhIn are found to show a ferromagnetic half-metallic behavior with a total magnetic moment 2μB, which agrees with the generalized Slater-Pauling rule. The formation energy for both Zr2RhGa and Zr2RhIn Heusler alloys are calculated and found to be equal to −0.129929 Ry and −0.110681 Ry, respectively, which means in principle they could be synthesized in laboratories. We further investigate the stabilities of the two alloys by calculating the mechanical and elastic properties which showed that both alloys are mechanically stable. Using the mean _eld approximation we were able to estimate the Curie temperature which turned out to be 536.28 K for Zr2RhGa and 972 K for Zr2RhIn. Thermoelectric behavior is studied using the BoltzTrap code, both systems show good thermoelectric properties for the spin down channel, however utilizing the two-current model the properties are not good enough for conventional thermoelectric materials.

Origin of half-metallicity in XCrBi (X = Hf,Ti, and Zr) half-Heusler alloys

First principles calculation has been employed to investigate the physical properties and thermodynamic properties of XCrBi (X = Hf, Ti and Zr) half-Heusler alloys. The half Heusler alloys TiCrBi and ZrCrBi studied are found to possess half-metallic character except HfCrBi showing metallic behaviour in both spin up and spin down channel. The Slater-Pauling rule is uesd to predicted the total magnetic moment of 3μB which confirmed the values from calculation. All half Heusler alloys are mechanically and thermodynamically stable.

Investigation of structural, electronic, magnetic and mechanical properties of a new series of equiatomic quaternary Heusler alloys CoYCrZ (Z = Si, Ge, Ga, Al): A DFT study

The structural stability, band structure, density of states (DOS), magnetic and mechanical properties of Co-based equiatomic quaternary Heusler alloys (EQHAs) CoYCrZ (Z = Si, Ge, Ga, Al) are examined by employing 1st principle calculations in the framework of density functional theory (DFT) as embedded in Wien2k code. The generalized gradient approximation (GGA) of Perdew-Burke Ernzehrof (PBE) is used for all these calculations. The lattice constants obtained by the optimization of structures and Type-II is found the most stable configuration for all alloys. The band diagrams and DOS calculations show that all these materials possess half metallic (HM) character because they have band gap in minority spin channel. The origin of band gap has been explained which is due to the robust d-d hybridization among transition metals (TMs). The obtained magnetic moments (MMs) are in accordance to the Slater-Pauling rule. The considered materials have high MMs and all alloys showed 100% spin polarization (SP). Curie temperature has also been calculated and reported for all these alloys. In order to check the mechanical stability, the calculations for elastic constants and other mechanical parameters are carried out which have revealed that all alloys are stable and have ductile nature. All the considered alloys in this study are reported for the first time and no data is available for comparison. It is envisaged these alloys are suitable for spintronic applications as in magnetic tunnel junctions (MTJs), spin valves, and spin injectors etc.

Ab-initio study of electronic and magnetic properties of CoIrMnZ (Z = Al, Si, Ga, Ge) Heusler alloys

Using first principles calculations based on density functional theory, we study electronic and magnetic properties of CoIrMnZ (Z = Al, Si, Ga, Ge) Heusler systems. Based on the electronic structure calculations, CoIrMnSi and CoIrMnGe are predicted to be half-metallic. For the studied systems, the ground state magnetic configurations are found to be ferromagnetic with magnetic moment consistent with the Slater-Pauling rule. The calculated ferromagnetic transition temperatures are much higher than the room temperature for all the cases. The effect of spin orbit coupling has been discussed on the electronic structure for all the systems studied here. Furthermore, we construct junctions with MgO along (001) direction. The MnZ terminations are found to be energetically more favourable compared to the CoIr terminations. After discussing the tunnelling conductance, we find that CoIrMnSi/MgO/CoIrMnSi could be a promising magnetic tunnelling junction (MTJ) candidate.

First-principles Predictions on Half-Metallic, Mechanical, and Acoustic Properties of CuHg2Ti-Type Mn2LiZ (Z=As, Sb) Compounds

Using first-principles calculations, we predicted the half-metallic, mechanical, and acoustic properties of novel CuHg2Ti-type Mn2LiZ (Z=As, Sb) compounds. It was found that Mn2LiAs and Mn2LiSb are half-metallic ferrimagnetic compounds with gaps in the minority-spin direction of 1.094 and 1.099 eV in equilibrium state, respectively, and have an integer total magnetic moments of 2.000 μB per formula unit for adherence to the Slater-Pauling rule. It was also found that Mn2LiAs and Mn2LiSb are mechanically stable, brittle, and elastically anisotropic, and Mn2LiAs has more brittleness, more significant anisotropy, and higher Debye temperature than Mn2LiSb.

Computational study of the electronic, magnetic, mechanical and thermodynamic properties of new equiatomic quaternary heusler compounds TiZrRuZ (Z = Al, Ga, In)

The electronic, magnetic, and mechanical properties of the new equiatomic quarternary Heusler compounds TiZrRuZ (Z = Al, Ga, In) have been studied with the first-principles calculations. Three types of different atomic configurations have been examined and results show the atomic site occupation follows the general site preference rule. The equilibrium lattice constants have been determined and also the total and atom-resolved magnetic moments have been calculated. These new equiatomic quarternary Heusler compounds TiZrRuZ (Z = Al, Ga, In) are ferromagnetic half metals at the ground states. In particular for the total magnetic moment (MT), an integral number of 1 µB is obtained with the main contribution from Ti atoms and it follows the general Slater-Pauling rule, i.e. MT = ZT -18, where ZT is the total valence electron number, 19 for TiZrRuZ. Furthermore, the derived mechanical properties have shown that these materials behave in a strong ductile manner with a high elastic anisotropy, which is further confirmed by the calculated 3D Young's modulus and shear modulus. Their mechanical and dynamic stabilities have also been verified with the generalized elastic criteria and phonon dispersion spectrum. Afterwards, the effects of the uniform and tetragonal strains have been studied. The variation of the conduction band minimum and the valence band maximum with both strains have been revealed and the materials show good robustness of the half metallicity. Also, the total magnetic moment maintains constant of 1 µB against both strains while the atomic magnetic moments vary. In the last, the thermodynamic properties have also been analyzed with the quasi-harmonic Debye model under pressure 0 to 10 GPa and temperature from 0 to 500 K. These materials can be good candidates for the future spintronic application and can even inspire other relative work for material research in this field.