Quaternary Heusler Compounds Research Articles

Electronic, magnetic, mechanical, half-metallic and highly dispersive zero-gap half-metallic properties of rare-earth-element-based quaternary Heusler compounds

Finding novel half-metallic materials (HMMs) with Heusler structure is a focus of current research. Therefore, in this work, we aim to predict new HMMs in some rare-earth-element-contained equiatomic quaternary Heusler (EQH) compounds by using the first-principle calculations. In detail, the structural, electronic, magnetic, mechanical and half-metallic properties of LuFeMnZ (Z = Al, Ga), YFeMnZ (Z = Al, Ga), LuCoCrZ (Z = Si, Ge) and LaCoCrAl compounds were investigated. The calculated results showed that all the above-mentioned compounds are HMMs with complete spin polarisation around the Fermi level. The half-metallic behaviour, the spin-flip gaps and the total and atomic magnetic moments of these compounds for different lattice constants were also studied in detail. LuCoCrSi and LuCoCrGe compounds showed the largest spin-flip gaps of 0.42 eV at its equilibrium lattice constant and 0.39 eV at its strained lattice constant, respectively. Importantly, HMMs with a unique zero gap in one spin channel have also drawn much research attention in recent years. In the current work, the highly dispersive zero-gap half-metallic properties of LuCoCrGe compound were observed, when its lattice constant was extended to 6.70 and 6.80 Å. Finally, the mechanical stability and the phase stability of the above-mentioned compounds were analysed in detail.

New quaternary half-metallic ferromagnets with large Curie temperatures

New magnetic materials with high Curie temperatures for spintronic applications are perpetually sought for. In this paper, we present an ab initio study of the structural, electronic and magnetic properties of Quaternary Heusler compounds CoX′Y′Si where X′ is a transition metal with 4d electrons and Y′ is either Fe or Mn. We find five new half-metallic ferromagnets with spin polarisation nearly 100% with very high Curie temperatures. The variation of Curie temperatures as a function of valence electrons can be understood from the calculated inter-atomic exchange interaction parameters. We also identify a few other compounds, which could be potential half-metals with suitable application of pressure or with controlled doping. Our results reveal that the half-metallicity in these compounds is intricately related to the arrangements of the magnetic atoms in the Heusler lattice and hence, the interatomic exchange interactions between the moments. The trends in the atomic arrangements, total and local magnetic moments, interatomic magnetic exchange interactions and Curie temperatures are discussed with fundamental insights.

Highly-dispersive spin gapless semiconductors in rare-earth-element contained quaternary Heusler compounds

The acquisition of high mobility electrons in the zero-gap band of spin gapless semiconductors is crucial for their practical applications in spintronic devices. In this work, we propose to design a higher dispersive band by importing the rare-earth atom into the Heusler compounds. With first principles calculations, we identify several new spin gapless semiconductor candidates in the 21-electron LiMgPdSn-type quaternary Heusler alloys of (Y, La, Lu)CoCr/FeMn(Al, Ga). Densities of states for most of them reveal large band gaps in the minority spin direction, and relatively low states near the Fermi level in the majority spin. According to the electron projected band analysis, we find the import of the rare earth atom can enhance the sp component in the band across the Fermi level, which is conducive to form a linear-dispersive band that is promising to enhance the carrier mobility of spin gapless semiconductors.

First-principles study of new quaternary Heusler compounds without 3d transition metal elements: ZrRhHfZ (Z = Al, Ga, In)

Plane-wave pseudo-potential methods based on density functional theory are employed to investigate the electronic structures, and the magnetic and half-metallic properties of the newly designed quaternary Heusler compounds ZrRhHfZ (Z = Al, Ga, In) without 3d transition metal elements. The calculated results show that ZrRhHfZ (Z = Al, Ga, In) compounds are half-metallic, with 100% spin polarization around the Fermi level. The structural stability of these compounds has been tested from the aspects of their cohesion energy and formation. The spin-flip/half-metallic gaps of ZrRhHfZ (Z = Al, Ga, In) compounds are quite large, with values of 0.2548 eV, 0.3483 eV, and 0.2866 eV, respectively. These compounds show Slater-Pauling behavior, and the total spin magnetic moment per unit cell (Mt) scales with the total number of valence electrons (Zt) following the rule: Mt = Zt − 18. The magnetization of ZrRhHfZ (Z = Al, Ga, In) compounds mainly comes from the 4d electrons of the Zr atoms and the 5d electrons of the Hf atoms. Furthermore, the effects of uniform strain and tetragonal deformation on the half metallicity has been investigated in detail, which is important for practical application. Finally, we reveal that the half-metallicity can be maintained when the Coulomb interactions are considered.

Half-metallic ferromagnetism in KCaNX (X = O, S, and Se) quaternary Heusler compounds: A first-principles study

On the basis of ab initio calculations, we explored the electronic structures and magnetic properties of quaternary alloys KCaNX (X = O, S, and Se) with full-Heusler structure. Results showed that type-1 is the most favorable atomic arrangement where N, K, X, and Ca occupy (0, 0, 0), (0.25, 0.25, 0.25), (0.5, 0.5, 0.5), and (0.75, 0.75, 0.75) sites, respectively. All the compounds are found to be half-metallic ferromagnetic materials with an integer magnetic moment of 2.00 μB, which predominantly derives from the strong spin polarization of p channels of N hybridized with X elements. The predicted half-metallic gaps are 0.83, 0.81, and 0.82 eV for KCaNO, KCaNS, and KCaNSe, respectively. In addition, the calculated negative values of formation energies indicate that all these composites are thermodynamically stable and thus could be synthesized with appropriate experiment conditions in the future.

First-principles study on electronic structure, magnetism and half-metallicity of the NbCoCrAl and NbRhCrAl compounds

The electronic structure, magnetism and half-metallicity of quaternary Heusler compounds NbCoCrAl and NbRhCrAl were investigated theoretically by using first-principles calculations. It was found that the equilibrium lattice constants of NbCoCrAl and NbRhCrAl compounds are 6.02Å and 6.18Å, respectively. The total magnetic moment is 1μB and consistent with the Slater-Pauling formula: Mt=24−Zt. The half-metallicity can be kept when the lattice constant changes in the range of 5.87–6.07Å and 5.954–6.279Å for NbCoCrAl and NbRhCrAl compounds, respectively. The half-metallic band gap locates between the eu and t1u states originating from the hybridizations of the d states of Cr and Co (Rh) atoms. Compared with NbCoCrAl, as the radius of Rh with valance electron in 4d states is bigger than that of Co with valance electron in 3d states, NbRhCrAl has a more stable half-metallicity and bigger equilibrium lattice constant. In particular, the half-metallicity of NbRhCrAl is more robust against the lattice thermal expansion with increasing temperature.

Half-metallicity of the bulk and (001) surface of NbFeCrAl and NbFeVGe Heusler compounds: a first-principles prediction

Using first-principles calculations based on density-functional theory, the structural, electronic and magnetic properties in the bulk and (001) surfaces of quaternary Heusler compounds NbFeCrAl and NbFeVGe are investigated.

Synthesis of low-moment CrVTiAl: A potential room temperature spin filter

The efficient production of spin-polarized currents at room temperature is fundamental to the advancement of spintronics. Spin-filter materials—semiconductors with unequal band gaps for each spin channel—can generate spin-polarized current without the need for spin-polarized contacts. In addition, a spin-filter material with zero magnetic moment would have the advantage of not producing strong fringing fields that would interfere with neighboring electronic components and limit the volume density of devices. The quaternary Heusler compound CrVTiAl has been predicted to be a zero-moment spin-filter material with a Curie temperature in excess of 1000 K. In this work, CrVTiAl has been synthesized with a lattice constant of a = 6.15 Å. Magnetization measurements reveal an exceptionally low moment of μ = 2.3 × 10−3 μB/f.u. at a field of μ0H = 2 T that is independent of temperature between T = 10 K and 400 K, consistent with the predicted zero-moment ferrimagnetism. Transport measurements reveal a combination of metallic and semiconducting components to the resistivity. Combining a zero-moment spin-filter material with nonmagnetic electrodes would lead to an essentially nonmagnetic spin injector. These results suggest that CrVTiAl is a promising candidate for further research in the field of spintronics.

Ab-initio study of structural, elastic, thermal, electronic and magnetic properties of quaternary Heusler alloys CoMnCrZ (Z = Al, As, Si, Ge)

First-principles approach is used to study the structural, electronic and magnetic properties of CoMnCrZ (Z = Al, Si, Ge and As) quaternary Heusler compounds, using full-potential linearized augmented plane wave (FP-LAPW) scheme within the generalized gradient approximation (GGA). The computed equilibrium lattice parameters agree well with the available theoretical data. The obtained negative formation energy shows that CoMnCrZ (Z = Al, Si, Ge, As) compounds have strong structural stability. The elastic constants C ij are calculated using the total energy variation with strain technique. The polycrystalline elastic moduli (namely: the shear modulus, Young’s modulus, Poisson’s ratio, sound velocities, Debye temperature and melting temperature were derived from the obtained single-crystal elastic constants. The ductility mechanism for the studied compounds is discussed via the elastic constants C ij . Our calculations with the GGA approximation predict that CoMnCrGe, CoMnCrAl, CoMnCrSi and CoMnCrAs are half-metallic ferrimagnets (HMFs) with a half-metallic gap E HM of 0.03 eV, 0.19 eV, 0.34 eV and 0.50 eV for, respectively. We also find that the half-metallicity is maintained on a wide range of lattice constants.

The effect of pressure and alloying on half-metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

AbstractIn this work, first-principles calculations of the structural, electronic and magnetic properties of Heusler alloys CoMnYAl, CoMnYGa and CoMnYIn are presented. The full potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT) has been applied. The structural results showed that CoMnYZ (Z = Al, Ga, In) compounds in the stable structure of type 1+FM were true half-metallic (HM) ferromagnets. The minority (half-metallic) band gaps were found to be 0.51 (0.158), 0.59 (0.294), and 0.54 (0.195) eV for Z = Al, Ga, and In, respectively. The characteristics of energy bands and origin of minority band gaps were also studied. In addition, the effect of volumetric and tetragonal strain on HM character was studied. We also investigated the structural, electronic and magnetic properties of the doped Heusler alloys CoMnYGa1−xAlx, CoMnYAl1−xInxand CoMnYGa1−xInx(x = 0, 0.25, 0.5, 0.75, 1). The composition dependence of the lattice parameters obeys Vegard’s law. All alloy compositions exhibit HM ferromagnetic behavior with a high Curie temperature (TC).

Half-metallicity and magnetism of quaternary Heusler compounds CoRuTiZ (Z=Si, Ge, and Sn)

First-principle calculations based on the density functional theory for new quaternary Heusler compounds CoRuTiZ (Z=Si, Ge, and Sn) were performed. It was found that all three compounds were stable at YI structure in ferromagnetic state. The CoRuTiSi, CoRuTiGe, and CoRuTiSn were half-metal with integer magnetic moments of 1.00 μB per formula unit and half-metallic gaps of 0.13, 0.10, and 0.01eV at their equilibrium volume, respectively. The density of states (DOSs) and band structures of these compounds were studied and the origin of half-metallicity was discussed. The CoRuTiSi, CoRuTiGe, and CoRuTiSn compounds showed half-metallic characteristics at lattice constants ranges of 5.77–6.36Å, 5.66–6.16Å, and 5.83–6.23Å, indicating the lattice distortion did not affect the half-metallic properties of these compounds which makes them interesting materials in the spintronic field.

First-principles study on the half-metallic properties of the d quaternary Heusler compounds: KCaCBr and KCaCI

With ab initio calculations, we studied the structural, electronic, and magnetic properties of quaternary Heusler compounds KCaCX (X = Br and I) adopted stable and metastable phases. We found that the most stable structure is type-3 atomic arrangement configuration where K, Ca, C, and X atoms occupy (0, 0, 0), (0.5, 0.5, 0.5), (0.25, 0.25, 0.25) and (0.75, 0.75, 0.75) positions, respectively. The metastable one is type-1 configuration where K, C, Ca and X occupy (0, 0, 0), (0.5, 0.5, 0.5), (0.25, 0.25, 0.25) and (0.75, 0.75, 0.75) positions, respectively. The results show that they are half-metallic ferromagnets with integer magnetic moments of 2.0 μB at their equilibrium lattice constants. It is also found that the spin-polarization is mainly from the C-2p states. In addition, KCaCBr compound with type-1 configuration shows an electronic transition from ordinary half-metallic state to zero-gap half-metallic state with the changing the lattice parameter.

First-principles study of structural, elastic, thermodynamic, electronic and magnetic properties for the quaternary Heusler alloys CoRuFeZ (Z = Si, Ge, Sn)

The electronic structure and magnetic properties of CoRuFeZ (Z = Si, Ge, and Sn) quaternary Heusler compounds were investigated using the full-potential linearized augmented plane wave (FPLAPW) method in framework of the density functional theory (DFT). The results showed that CoRuFeZ (Z = Si, Ge, and Sn) compounds were stable in Y-type1 structure. By use the GGA-mBJ, the CoRuFeGe and CoRuFeSn compounds were true half-metallic (HM) ferromagnets. The CoRuFeSi had a nearly HM characteristic. The minority band gaps were 0.557 eV, 0.444 eV and 0.428 eV for CoRuFeSi, CoRuFeGe and CoRuFeSn, respectively. The total magnetic moments of CoRuFeGe and CoRuFeSn compounds were obtained 5 μB per formula unit, which were in agreement with Slater-Pauling rule Mtot = (Ztot − 24). CoFeTiSi alloy can transform from a nearly half-metallic to a half-metallic alloy by employing a little expansion stress (+1.725% relatively to the equilibrium lattice constant a0). The half-metalliciy characteristic exists in relatively wide ranges of 5.9–6.9 Å, 5.825–6.063 Å and 5.921–7.187 Å for CoRuFeSi, CoRuFeGe and CoRuFeSn compounds, respectively, which makes them promising candidates in spintronics.

First-principles study of new series of quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb)

The structural, electronic, magnetic, and thermal properties of new quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb) were investigated using the full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA) and GGA plus modified Becke and Johnson as the exchange correlation. The results showed that all Heusler compounds were stable in Type (I) structure. The CsSrCZ (Z=Si, Ge, Sn) compounds had a nearly HM characteristic, and CsSrCZ (Z=P, As, Sb) compounds were true half-metallic (HM) ferromagnets. The strong spin polarization of p orbital for C, Si, Ge, Sn, P, As, and Sb atoms is found to be the origin of ferromagnetic. The half-metallicity is preserved up to a lattice contraction of 3.45%, 1.69%, 1.69%, 7.16%, 7.16%, and 11.2% for all six quaternary Heusler compounds. We also investigated the thermal effects using the quasi-harmonic Debye model.

Spin-filter and spin-gapless semiconductors: The case of Heusler compounds

We review our recent first-principles results on the inverse Heusler compounds and the ordered quaternary (also known as LiMgPdSn-type) Heusler compounds. Among these two subfamilies of the full-Heusler compounds, several have been shown to be magnetic semiconductors. Such material can find versatile applications, e.g. as spin-filter materials in magnetic tunnel junctions. Finally, a special case are the spin-gapless semiconductors, where the energy gap at the Fermi level for the one spin-direction is almost vanishing, offering novel functionalities in spintronic/magnetoelectronic devices.

First-principles Study on Half-metallic Properties of the CoMnCrSb Quaternary Heusler Compound

Within the framework of density functional theory, the electronic structure and magnetic properties have been studied for the CoMnCrSb quaternary Heusler compound. Features such as the lattice constant, the bulk modulus, and its pressure derivative are reported. The spin-up band of compound has metallic character, and spin-down band is semiconducting with an indirect gap of 0.50 eV at equilibrium lattice constant, resulting in stable half-metallic ferrimagnetic behavior with a magnetic moment of 3 μB. In addition, the ferromagnetic states are found to be energetically more favorable than paramagnetic states. Therefore, the CoMnCrSb compound is a candidate material for future spintronic application.

The effect of a fourth element (Co, Cu, Fe, Pd) on the standard enthalpy of formation of the Heusler compound Ni2MnSn

The standard enthalpies of formation of quaternary Heusler compounds (X, Ni)2MnSn (X = Co, Cu, Fe, Pd) were investigated experimentally using high temperature direct reaction calorimetry. Lattice parameters of these compounds were determined using X-ray diffraction analysis. Microstructures were identified using scanning electron microscopy and energy dispersive spectroscopy. The effect of an additional X element on the standard enthalpy of formation of the Heusler compound Ni2MnSn is discussed.

Origin of the half-metallic band-gap in newly designed quaternary Heusler compounds ZrVTiZ (Z = Al, Ga)

In this work, first-principles calculations have been used to investigate the electronic structures, magnetic properties, and half-metallic nature of the newly designed quaternary Heusler compounds ZrVTiAl and ZrVTiGa.

Recent advances in the Heusler based spin-gapless semiconductors

In this work, we review the progress on the Heusler-based materials with spin-gapless semiconducting behaviour, including half-Heusler compounds, full-Heusler compounds, DO3-type compounds, and LiMgPdSn-type quaternary Heusler compounds.

First-principles study on quaternary Heusler compounds ZrFeVZ (Z = Al, Ga, In) with large spin-flip gap

First-principles calculations were used to systematically investigate the structural, electronic and half-metallic properties of newly designed quaternary Heusler compounds ZrFeVZ (Z = Al, Ga, In).