Half-metallic Ferrimagnets Research Articles

Half-Metallic Properties of the Mn2Te Telluride by a First-Principles Study

The electronic band structure, magnetic properties, and half-metallic properties of the Mn2Te compound in the C1b-type, CaF2-type, and Ni2In-type structures have been studied by using the full-potential linearized augmented plane wave (FPLAPW) method within the generalized gradient approximation (GGA). The ferrimagnetic ground state of the Mn2Te compound is the most stable with the C1b-type structure. The value of total magnetic moment, 2 μ B/f.u. at the equilibrium lattice constant a 0= 5.92 A, agrees with the Slater–Pauling rule for the C1b-type Mn2Te compound. The Mn2Te compound with the C1b-type structure is found to be a half-metallic ferrimagnet with a half-metallic band gap of 1.19 eV. Half metallicity is kept for a broad range of lattice constants below 6.13 A. The Curie temperature for the C1b-type structure is calculated to be 1231 K in the mean field approximation (MFA).

Half-metallic completely compensated ferrimagnets in Cr doped BaP

On the basis of ab-initio calculations we have investigated the electronic and magnetic properties of Cr1-xBaxP alloy, our calculations suggest that as we dope BaP with Cr atoms and move towards Cr1-xBaxP where x=0, 0.125, 0.25, 0.50, and 0.75 all alloy are HM-FM. Interestingly Cr0.25Ba0.75P is a HM-AFM otherwise ‘fully compensated ferrimagnet’, this alloy should be of special interest for applications since it creates no external stray field and thus exhibit minimal energy losses. In addition, the robustness of half-metallicity with respect to the variation of lattice constants of Cr1-xBaxP is also discussed; moreover ferrimagnetism co-exists with the half-metallicity, resulting in the desired fully compensated half-metallic ferrimagnetism, for a wide range of lattice constants. Furthermore we found that this new HMFCF is stable according to its small formation energy.

Magnetism and Half-Metallicity in the Fe2ZrP Heusler Alloy

The electronic structure and magnetic properties of the Fe2ZrP full-Heusler compound has been investigated by using ab initio calculations with the full-potential linearized augmented plane wave (FLAPW) method. The exchange-correlation functionals are taken into account within the generalized gradient approximation (GGA). Energetically, the AlCu2Mn-type structure of the full-Heusler Fe2ZrP is energetically more preferable than that of the CuHg2Ti-type structure and it exhibits half-metallic ferrimagnet. The calculated total spin moment is found as 1 μ B at the equilibrium lattice constant a 0=5.90A which remarkably agrees with the Slater-Pauling rule of M t = Z t −24. While the spin-up band is metallic, the spin-down band has a semiconductor behavior with a gap of 0.593 eV and the spin-flip gap is 0.129 eV. The negative formation energy is shown as an evidence of the thermodynamic stability of alloy. The dependencies of the magnetic and electronic properties on the lattice constant are also discussed. The estimated Curie temperature is 752 K in the mean field approximation.

The structural, electronic, magnetic and mechanical properties of quaternary Heusler alloys ZrTiCrZ (Z = Al, Ga, In, Si, Ge, Sn): a first-principles study

The structural, electronic, magnetic and mechanical properties of the quaternary Heusler alloys ZrTiCrZ (Z = Al, Ga, In, Si, Ge, Sn) have been investigated firstly by using the first-principles calculations. The preferred configurations of the ZrTiCrZ alloys are all Y-type (I). At their equilibrium lattice constants, the ZrTiCrZ alloys are half-metallic (HM) ferrimagnets for Z = Al, Ga and In, while spin-gapless semiconductor (SGS) antiferromagnets (AFM) for Z = Si, Ge and Sn. The total magnetic moments of the ZrTiCrZ alloys are −1 for Z = Al, Ga and In, while 0 for Z = Si, Ge and Sn, both linearly scaled with the total number of valence electrons by Slater–Pauling rule . The elastic constants , and of the single crystal and the related elastic moduli , , , and of the polycrystalline aggregates are also calculated and used to study the mechanical stability of these alloys. Although the Curie temperatures of the ZrTiCrZ alloys are overestimated by using the mean field approximation (MFA), they can be better estimated by including the exchange interactions. Finally, the HM stabilities as well as the total and atomic magnetic moments of the ZrTiCrZ alloys (Z = Al, Ga, In) under either hydrostatic strain or tetragonal strain are also discussed.

Possible half-metallic antiferromagnetism in an iridium double-perovskite material

Using the first-principles density functional approach, we investigate a material Pr$_2$MgIrO$_6$ (PMIO) of double perovskite structure synthesized recently. According to the calculations, PMIO is a magnetic Mott-Hubbard insulator influenced by the cooperative effect of spin-orbit coupling (SOC) and Coulomb interactions of Ir-5$d$ and Pr-4$f$ electrons, as well as the crystal field. When Pr is replaced with Sr gradually, the system exhibits half metallic (HM) states desirable for spintronics applications. In [Pr$_{2-x}$Sr$_x$MgIrO$_6$]$_2$, HM antiferromagnetism (HMAFM) with zero spin magnetization in the unit cell is obtained for $x=1$, whereas for $x=0.5$ and 1.5 HM ferrimagnetism (HMFiM) is observed with $\mu_{\rm tot}=3\mu_{\rm B}$ and $\mu_{\rm tot}=-3\mu_{\rm B}$ per unit cell respectively. It is emphasized that the large exchange splitting between spin-up and spin-down bands at the Fermi level makes the half metallicity possible even with strong SOC.

Designing a fully compensated half-metallic ferrimagnet

Recent experimental work on Mn2RuxGa demonstrates its potential as a compensated ferrimagnetic half-metal (CFHM).Here we present a set of high-throughput ab initio density functional theory calculations and detailed experimental characterisation, that enable us to correctly describe the nominal Mn2RuxGa thin films, in particular with regard to site-disorder and defects. We then construct models that accurately capture all the key features of the Mn-Ru-Ga system, including magnetic compensation and the spin gap at the Fermi level. We find that electronic doping is neccessary, which is achieved with a Mn/Ga ratio smaller than two. Our study shows how composition and substrate-induced biaxial strain can be combined to design the first room-temperature CFHM.

Structural disorder and magnetism in the spin-gapless semiconductor CoFeCrAl

Disordered CoFeCrAl and CoFeCrSi0.5Al0.5 alloys have been investigated experimentally and by first-principle calculations. The melt-spun and annealed samples all exhibit Heusler-type superlattice peaks, but the peak intensities indicate a substantial degree of B2-type chemical disorder. Si substitution reduces the degree of this disorder. Our theoretical analysis also considers several types of antisite disorder (Fe-Co, Fe-Cr, Co-Cr) in Y-ordered CoFeCrAl and partial substitution of Si for Al. The substitution transforms the spin-gapless semiconductor CoFeCrAl into a half-metallic ferrimagnet and increases the half-metallic band gap by 0.12 eV. Compared CoFeCrAl, the moment of CoFeCrSi0.5Al0.5 is predicted to increase from 2.01 μB to 2.50 μB per formula unit, in good agreement with experiment.

Half-Metallic Properties of the Ru2ZrSb Full-Heusler Compound: a First-Principles Study

A first-principles study on the electronic structure and magnetic properties of the Ru2ZrSb Heusler compound has been performed by using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. It is found that the AlCu2Mn-type structure exhibits half-metallic ferrimagnetism and is preferable energywise than the CuHg2Ti-type structure. The total spin magnetic moment is based on mainly the Ru atoms and obeys the Slater-Pauling rule. The calculated total magnetic moment of Ru2ZrSb is −1.0 μ B at the equilibrium lattice constant 6.497 A for the AlCu2Mn-type structure. The spin-down electrons are metallic, but the spin-up bands are semiconductor with a gap of 0.388 eV, and the spin-flip gap is 0.313 eV. The AlCu2Mn-type Ru2ZrSb Heusler compound keeps a 100 % of spin polarization for lattice constants ranging between 6.40 and 6.53 A. The Curie temperature is estimated to be 322.7 K in the mean field approximation (MFA).

First-principles Investigation of Half-metallicity and Ferrimagnet Properties of Co2ScZ (Z = As, Sb, and Bi)

Based on the first-principles methods, the half-metallic ferrimagnet properties of Co2ScZ (Z = As, Sb, and Bi) full-Heusler alloys have been predicted by employing the full-potential linearized plane wave plus local orbital method (FP-LAPW + lo) within the framework of density functional theory (DFT) and generalized gradient approximation plus Coulomb repulsion (GGA + U) parameterization. The GGA scheme is served in this work to obtain only the equilibrium structural parameters in both paramagnetic and ferromagnetic phases, whereas the GGA + U scheme is exploited to treat the “d” electrons through electronic and magnetic properties of these Heusler alloys. The electronic structure investigation shows that all Co2ScAs, Co2ScSb, and Co2ScBi Heusler alloys are stable half metals with half-metallic gap energies (EHM) of 0.351, 1.080, and 0.836 eV, respectively. The total magnetic moment follows the generalized Slater-Pauling rule, where its value is around 2 μB for all these compounds. We have also found opposite signs between atomic magnetic moments of Co and Sc transition elements, demonstrating the ferrimagnetic behavior.

Prediction of the Half-Metallic Properties of Zr2VZ (Z = Si, Ge, Sn, and Pb) Heusler Alloys Based on Density Functional Theory

Density functional theory plane-wave pseudo-potential methods were used to study the electronic structures, magnetic properties, and half-metallic nature of Zr 2VZ (Z = Si, Ge, Sn, and Pb) alloys. Electronic-structure calculations show that the Zr 2VZ (Z = Si, Ge, Sn, and Pb) alloys in the AlCu 2Mn-type structure are conventional ferrimagnets. However, in the CuHg 2Ti-type structure, these alloys are half-metallic ferrimagnets. In addition, the half-metallic states and magnetism versus the lattice constant of the Zr 2VZ (Z = Si, Ge, Sn, and Pb) alloys in the CuHg 2Ti-type structure have been tested. The calculated total magnetic moment of the Zr 2VZ (Z = Si, Ge, Sn, and Pb) alloys in the CuHg 2Ti type is 1 μ B per unit cell, which is in line with the Slater-Pauling curve of the total magnetic moment (M t) = 18 − Z t.

Robust half-metallic properties in inverse Heusler alloys composed of 4d transition metal elements: Zr2RhZ (Z=Al, Ga, In)

A first-principles approach is used to study the electronic and magnetic properties of Zr2RhZ (Z=Al, Ga, In) alloys in the Hg2CuTi-type structure. The Zr2RhZ (Z=Al, Ga, In) alloys are found to be half-metallic ferrimagnets. The half-metallicity is quite robust against hydrostatic strain and tetragonal deformation in Zr2RhZ (Z=Al, Ga, In) alloys. The magnetization of Zr2RhZ (Z=Al, Ga, In) alloys mainly originates from the 4d electrons of Zr atoms and follows the rule: Mt=Zt−18. Zr2Rh-based alloys do not contain any 3d transition metal element, which implies a wider field to search for new half-metallic materials.

Half-Metallicity and Tetragonal Deformation of Ti2RhAl, Ti2RhGa, and Ti2RhIn: A First-Principle Study

Plane-wave pseudo-potential methods based on density functional theory are used to study the electronic structures, magnetic properties, and half-metallicity of new predicted Ti2-based full Heusler alloys Ti2RhZ (Z = Al, Ga, In). The CuHg2Ti-type structure is observed to be more favorable than the AlCu2Mn-type structure for these alloys. They are half-metallic ferrimagnets with total magnetic moment of 2.00 μ B per formula unit and follow the Slater-Pauling rule. Also, results show that these Ti2RhZ (Z = Al, Ga, In) alloys have an indirect band gap with values of 0.577, 0.696, and 0.616 eV, respectively, in the minority spin channel. Two types of structural changes are used to test the sensitivity of half-metallicity. Moreover, the whole alloys investigated in the current work have a negative formation energy, which means they are thermodynamically stable.

Half-Metallic Ferrimagnetism in the Mn2NbAl Full-Heusler Compound: a First-Principles Study

A first-principles study of the electronic structure and magnetic properties of the Heusler compound Mn 2NbAl has been performed. The calculations have been performed by using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. It is found that the AlCu 2Mn-type structure is preferable energy wise than the CuHg 2Ti-type structure and exhibits half-metallic ferrimagnetism. The calculated total magnetic moment of Mn 2NbAl is 2 μB at the equilibrium lattice constant of 6.005 A for the AlCu 2Mn-type structure. The total spin magnetic moment obeys the Slater-Pauling rule and is based on mainly the Mn atoms. The spin-down electrons are metallic, but the spin-up bands are semiconductor with a gap of 0.37 eV, and the spin-flip gap is of 0.09 eV. The AlCu 2Mn-type Mn 2NbAl full-Heusler compound keeps 100 % of spin polarization for lattice constants ranging between 5.93 and 6.20 A. The Curie temperature is estimated to be 994 K in the mean field approximation (MFA).

Antisite-induced half-metallicity and fully-compensated ferrimagnetism in Co–Mn–V–Al alloy

We predicted that Co–Mn–V–Al alloy is a fully-compensated half-metallic ferrimagnet in CoVMnAl-type atomic arrangement with 25% ∼ 50% Co–Mn antisites using band structure calculations. The CoVMnAl-type atomic arrangement with about 30% Co–Mn antisites was successfully synthesized. The measurements of magnetic properties and electronic transport properties confirmed the half-metallicity and fully-compensated ferrimagnetism. We argued that the half-metallicity and ferrimagnetism in Co–Mn–V–Al compounds originate from the antisite between the Co and Mn atoms, which implies a new way to search for half-metallic material in Heusler alloys.

Theoretical investigations of electronic structures, magnetic properties and half-metallicity in Heusler alloys Zr2VZ (Z = Al, Ga, In)

The electronic structures, magnetic properties and half-metallicity of Zr2VZ (Z = Al, Ga, In) bulk materials were investigated through first-principles calculations. Band structure calculations showed that Zr2VZ (Z = Al, Ga, In) alloys with an AlCu2Mn-type structure were conventional ferrimagnents. However, Zr2VZ (Z = Al, Ga, In) alloys with a CuHg2Ti-type structure were predicted to be half-metallic ferrimagnets that were quite robust against hydrostatic strain and tetragonal deformation. The total magnetic moment of the Zr2VZ (Z = Al, Ga, In) alloys with a CuHg2Ti-type structure was 2 µB per formula unit and followed the conventional Slater-Pauling rule: Mt = 18 - Zt. (Mt is the total magnetic moment per unit cell and Zt is the valence concentration) Furthermore, the origin of the band gap in the Zr2VZ (Z = Al, Ga, In) alloys was also well studied. All of these results indicate that these alloys, when they are successfully prepared, are good candidates for practical applications in spintronics.

Electronic structures, magnetic properties and half-metallicity in Heusler alloys Zr2IrZ (Z = Al, Ga, In)

The electronic structures, magnetic properties and half-metallicity in Zr2IrZ (Z = Al, Ga, In) alloys with the Hg2CuTi-type structure were systematically investigated by using the first-principle calculations. Zr2IrZ (Z = Al, Ga, In) alloys are predicted to be half-metallic ferrimagnets which are quite robust against hydrostatic strain and tetragonal deformation. The total magnetic moment of Zr2IrZ (Z = Al, Ga, In) alloys mainly originates from the 4d electrons of Zr atoms and follows the conventional Slater-Pauling rule: Mt = Zt−18. (Mt is the total magnetic moment per unit cell and Zt is the valence concentration). The origin of the band gap for Zr2IrZ (Z = Al, Ga, In) alloys is also well studied. Unconventionally, Zr2Ir-based alloys contain element with 5d valence electrons, which implies a wider field to search for new half-metallic materials.

The half-metallicity of LiMgPdSn-type quaternary Heusler alloys FeMnScZ (Z=Al, Ga, In): A first-principle study

Based on the first-principles calculations, quaternary Heusler alloys FeMnScZ (Z=Al, Ga, In) including its phase stability, band gap, the electronic structures and magnetic properties has been studied systematically. We have found that, in terms of the equilibrium lattice constants, FeMnScZ (Z=Al, Ga, In) are half-metallic ferrimagnets, which can sustain the high spin polarization under a very large amount of lattice distortions. The half-metallic band gap in FeMnScZ (Z=Al, Ga, In) alloys originates from the t1u-t2g splitting instead of the eu-t1u splitting. The total magnetic moments are 3μB per unit cell for FeMnScZ (Z=Al, Ga, In) alloys following the Slater–Pauling rule with the total number of valence electrons minus 18 rather than 24. According to the study, the conclusion can be drawn that all of these compounds which have a negative formation energy are possible to be synthesized experimentally.

Electronic structures, magnetic properties and half-metallicity in Heusler alloys Zr2CoZ (Z=Al, Ga, In, Sn)

The electronic structures, magnetic properties, and half-metallicity of full-Heusler alloys Zr2CoZ (Z=Al, Ga, In, Sn) with the Hg2CuTi-type structure have been studied by using the first-principles projector augmented wave (PAW) potential within the generalized gradient approximation (GGA). The Zr2CoZ (Z=Al, Ga, In, Sn) are found to be half-metallic ferrimagnets within a certain range of the lattice constant. The total magnetic moments (μt) of the Zr2CoZ alloys are calculated to be 2 for Z=Al, Ga, In and 3 for Z=Sn, linearly scaled with the total number of valence electrons (Zt) by μt=Zt−18. The origin of the band gap for these half-metallic alloys is well understood. These new Zr-based Heusler alloys are the ideal candidates for spintronic devices.

First principles study of a new half-metallic ferrimagnets Mn2-based full Heusler compounds: Mn2ZrSi and Mn2ZrGe

Half-metallic properties of new predicted Mn2-based full Heusler alloys Mn2ZrSi and Mn2ZrGe have been studied by first-principles full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method based on density functional theory (DFT). Our investigation is focused on the structural, elastic, electronic and magnetic properties of these compounds. The AlCu2Mn-type structure is found to be energetically more favorable than the CuHg2Ti-type structure for both compounds and are half-metallic ferrimagnets (HMFIs) with total magnetic moments of 2.000µB per formula unit, well consistent with Slater–Pauling rule (Mtot=(24–Ztot)µB). Calculations show that both the alloys have an indirect band gaps, in the majority-spin channel, with values of 0.505eV and 0.278eV for Mn2ZrSi and Mn2ZrGe, respectively. It was found that Mn2ZrSi and Mn2ZrGe preserved their half-metallicity for lattice constants range of 5.85–6.38Å and 6.05–6.38Å, respectively, and kept a 100% of spin polarization at the Fermi level. Moreover, the calculated formation energies and elastic constants confirm that these compounds are stable chemically and mechanically, and the good crystallographic compatibility with the lattice of semiconductors used industrially makes them promising magnetic materials in spintronic applications.

Phase stability, band gap, and electronic and magnetic properties of quaternary heusler alloys FeMnScZ (Z = Al, Ga, In)

By using the first-principles calculations, we have systematically investigated the phase stability, band gap, and electronic structures and magnetic properties of quaternary Heusler alloys FeMnScZ (Z = Al, Ga, In). We found that FeMnScZ (Z = Al, Ga, In) alloys are half-metallic ferrimagnets at their equilibrium lattice constants and retain a high spin polarization over a quite wide range of lattice distortions. The half-metallic band gap in the FeMnScZ (Z = Al, Ga, In) alloys arises from t 1u-t 2g splitting but not e u-t 1u splitting. The total magnetic moments are 3 µB per unit cell for FeMnScZ (Z = Al, Ga, In) alloys, following the Slater-Pauling rule with the total number of valence electrons minus 18 rather than 24. Moreover, all of these alloys have a negative formation energy, which implies that they can be synthesized experimentally.