Equiatomic Quaternary Heusler Alloy Research Articles

Structural, Electronic, Magnetic and Transport Properties of the Equiatomic Quaternary Heusler Alloys Cutcral (T = Co and Fe): Theory and Experiment

Structural, Electronic, Magnetic and Transport Properties of the Equiatomic Quaternary Heusler Alloys Cutcral (T = Co and Fe): Theory and Experiment

First-principles investigations of the half-metallic ferromagnetic LaCoTiIn equiatomic quaternary Heusler alloy for spintronics

We have evaluated the structural and mechanical stability, electronic structure, total spin magnetic moment, and Curie temperature of LaCoTiIn Equiatomic Quaternary Heusler Alloy (EQHA) using first-principles studies. The Generalized Gradient Approximation (GGA) and GGA+U schemes have been used as exchange-correlation functional for the above calculations. From the ground state calculation, LaCoTiIn EQHA with a Type-III structure in the ferromagnetic (FM) state is found to be stable. The electronic structure of LaCoTiIn EQHA depicts half-metallic behavior which has metallic overlap in the spin up ([Formula: see text] channel and a semiconductor band gap in the other channel. The spin–orbit coupling of LaCoTiIn has a great influence on the band gap of the material. The computed band gap values for the spin down ([Formula: see text] channel are 0.480 eV and 0.606 eV by using the GGA and GGA+U schemes. The total spin magnetic moment is 1 [Formula: see text], according to the Slater–Pauling rule, [Formula: see text] = ([Formula: see text] - 18) [Formula: see text]. These results obtained can be used as a valuable reference for future research, or they will be used to further motivate the experimental synthesis of the corresponding alloy.

Effect of pressure on dynamical stability, electronic and thermoelectric properties of equiatomic quaternary Heusler alloy LaCoTiGe

The equiatomic quaternary Heusler alloys have tremendous applications in many optoelectronic, thermoelectric, and spintronic devices. The proper functioning of these alloys requires the study of lattice dynamics at different values of pressure. Therefore, the lattice dynamical stability of Lanthanum-based LaCoTiGe quaternary Heusler alloy in the face-centered cubic phase has been explored under the effect of pressure by employing density functional perturbation theory followed by density functional theory. The lattice dynamical stability of the face-centered cubic phase of LaCoTiGe is computed with a uniform increase in pressure equal to 2.0 GPa. The pressure-dependent modes are observed in the F-43m phase at the ‘Г’ point. The calculated electronic band structure by implementing density functional theory shows the half-metallic character with a band-gap of the order 0.43 eV for stable LaCoTiGe in the minority spin channel. To evaluate the thermoelectric properties of LaCoTiGe at 2.0 GPa the Boltzmann approximation and constant time relaxation are incorporated as implemented in the BoltzTraP code. The half-metallic behavior of LaCoTiGe results in the high value of the Seebeck coefficient with its maximum value of −50 μV/K at 800K. At relatively higher values of temperature i.e., of the order of 800K, the calculated electronic thermoelectric figure of merit ZT for this material is 0.12, which is much higher than that of other reported similar quaternary Heusler alloys. Based on the results obtained, the Lanthanum-based quaternary Heusler alloy LaCoTiGe could be a suitable candidate for spintronic devices to operate under harsh environmental conditions.

Large Curie temperature and robust half metallicity of the CoRhMnSi equiatomic quaternary Heusler alloy

In this work, we study the structural, half-metallic behavior, exchange coupling interactions and the large Curie temperature of the equiatomic quaternary Heusler alloy CoRhMnSi, using the ab initio method. To predict the electronic properties of this alloy, we investigate the half-metallic behavior presented by the structure type II of the CoRhMnSi compound. Then, we compared the total magnetic moment (5.01 µB) of the studied alloy with that one estimated by the Slater–Pauling rule value (5.00 µB). Moreover, the studied material shows two different behaviors: a metallic one in the spin-up channel and a semi-conductor in the spin-down channel. In the later case, spin-down channel's corresponding band gap value is about 0.5 eV. Also, we found that the studied quaternary Heusler alloy CoRhMnSi reveals a robust half-metallic behavior. Conversely, our calculations revealed a Curie temperature value of the quaternary Heusler alloy CoRhMnSi close to

Structural, electronic and magnetic properties of the equiatomic quaternary Heusler CoRuMnGe alloy: a DFT study

In this paper, we investigate the structural, the electronic and the magnetic properties of the equiatomic quaternary Heusler alloy CoRuMnGe using the first-principle calculations. In fact, we apply the DFT method under Quantum Espresso package. For this purpose, we have examined the structural properties in order to determine the stability of the three configurations of this alloy: type I, type II and type III. Our calculations confirmed that the configuration of type I is the most stable one for the equiatomic quaternary Heusler alloy CoRuMnGe. Consequently, we have studied the electronic, magnetic properties and exchange coupling interactions only for the stable configuration. Also, we have illustrated the nearly half metallic behavior of this alloy, and deduced the rule Slater Pauling. On the other hand, following the mean-field approximation (MFA), we computed the Curie temperature value = 446.53 K for the studied compound.

Exploring the structural, elastic, lattice dynamical stability and thermoelectric properties of semiconducting novel quaternary Heusler alloy LiScPdPb

Quaternary Heusler alloy LiScPdPb with an 18-valence electron count show incredible applications in photovoltaic, spintronics, and thermoelectric materials. The study related to the structural, elastic, mechanical stability, and zone center phonon frequencies of LiScPdPb quaternary Heusler alloy is not investigated so far. Therefore, in the present article, the equiatomic quaternary Heusler alloy ‘LiScPdPb’ is studied in detail for their structural stability, elastic and mechanical stability. The research work presented in this report is undertaken by implementing first-principles Density Functional Theory (DFT). The non-magnetic character of the alloy is determined by the Slater-Pauling rule. Furthermore, density functional perturbation theory is implemented to calculate the phonon dispersion curves, phonon density of states, and zone center phonon frequencies of LiScPdPb. The calculated positive phonon frequencies have established the dynamical stability of LiScPdPb in the cubic phase. Raman and infrared phonon modes are also identified for the first time for LiScPdPb by implementing density functional perturbation theory. The calculated value of the bandgap is 0.22eV using generalized gradient approximations, while the bandgap of 1.62eV is observed by using Gaussian-Perdue-Burke–Ernzerhof (Gau-PBE) hybrid functional, which ensures the semiconducting nature of the alloy. In addition to the structural, elastic, mechanical, electronic, and lattice dynamical properties, the thermoelectric response of this alloy are also evaluated by including semi-classical Boltzmann transport theory. The maximum value of the obtained figure of merit for LiScPdPb is 0.18 ​at 1200 ​K, which opens up new avenues for its applications in electronic industries. Hence, the present work will provide a fertile field for the experimental researchers to synthesis this alloy for thermoelectric applications.

Novel half-metallicity in Y-type equiatomic quaternary Heusler alloys XFeCrAl (X = Rh, Pd, and Pt)

In the present study, we performed theoretical investigations to understand the origin of the half-metallic properties of new types of equiatomic quaternary Heusler compounds XFeCrAl (X = Rh, Pd, and Pt) and their possible applications in spintronics. These compounds crystallize in the Y-type structure with the F-43m space group, where the constitutive atoms are located in their non-equivalent positions in Type-I. Furthermore, we verified the thermodynamic, chemical, mechanical, and dynamical stabilities of these alloys. The results showed that they are stable in the magnetic phase where the optimized lattice constants are X-dependent. Among the three sample alloys, PdFeCrAl was shown to be the hardest with a brittle nature, whereas the others were found to be ductile. Analyses of the energy bands and magnetic profiles indicated the 100% spin-polarized, half-metallic, ferromagnetic natures of PdFeCrAl and PtFeCrAl, with EHM values of 0.09 eV and 0.03 eV, respectively, whereas RhFeCrAl is a nearly half-metallic ferrimagnet with 91% spin-polarization and it tends to act as a half-metal under the effect of uniform pressure. Their half-metallic nature can be expected because of the wide range of uniform strain due to their high bulk moduli. Thus, they have novel characteristics with lattice constants in the ranges of 5.55–5.64 Å, 5.53–6.04 Å, and 5.55–5.99 Å for RhFeCrAl, PdFeCrAl, and PtFeCrAl, respectively. The total magnetic moments of 1.98 μB, 2.99 μB, and 3.0 μB per formula unit obtained for RhFeCrAl, PdFeCrAl, and PtFeCrAl follow the Slater–Pauling rule. The highest Curie temperature (1113 K) obtained for PtFeCrAl demonstrates its feasible applications in spintronics with a high temperature limit.

A DFT study of the equiatomic quaternary Heusler alloys ZnCdXMn (X=Pd, Ni or Pt)

In this manuscript, we investigate the structural, electronic and magnetic properties of the quaternary Heusler alloys ZnCdXMn (X = Pd, Ni or Pt) by using the first-principle calculations. In fact, we explore the competing structure on the magnetic and electronic properties of the Zn-based equiatomic quaternary Heusler alloys ZnCdXMn (X = Pd, Ni or Pt) using the Ab-initio method. On the other hand, we have executed this method in order to determine not only the structural properties, but also the magnetic and the electronic properties of these alloys. The motivation of this work is to improve the competition between the austenitic and martensitic phases on the magnetic and electronic properties of the equiatomic quaternary Heusler Alloys ZnCdXMn (X = Pd, Ni or Pt), and their half-metallic behavior for the austenitic structure and 100% SP polarization. These alloys are useful in the spintronic devices uses.

Structural and magnetic properties of CoIrMnAl equiatomic quaternary Heusler alloy epitaxial films designed using first-principles calculations

• CoIrMnAl was computationally designed as one of the advanced materials for spintronics. • We obtained B2 ordered CoIrMnAl thin films with the lattice constant similar to that predicted in fully ordered alloy. • Magnetization at 10 K and Curie temperature measured were about 70% of the predicted values in fully ordered alloys. • Experimental data were well explained with ferrimagnetism due to Co-Mn swap disorders predicted from ab-initio calculation. MgO-barrier magnetic tunnel junctions with half-metallic Heusler alloy electrodes have attracted considerable attention for spintronics applications. However, there remain a couple of issues related to materials that should be resolved before practical use. Recently, quarterly equiatomic Heusler alloys have attracted attention as advanced Heusler alloys. CoIrMnZ (Z = Al, Si, Ga, and Ge) half-metallic Heusler alloys were designed and predicted to have moderate Curie temperatures and to be lattice-matched with the MgO barrier, which is advantageous compared to traditional Co 2 Heusler alloys T. T [T. Roy et al., J. Magn. Magn. Mater. 498 (2020) 166092]. Here, we experimentally investigated the structure and magnetic properties of thin films composed of one of these alloys, CoIrMnAl, fabricated by sputtering deposition. We successfully obtained films with the B 2 chemical ordering, even without a post-annealing process. The lattice constants for the films annealed at 500–600 ∘ C were approximately equal to the predicted values. The magnetization at 10 K was close to 500 kA/m, and the Curie temperature was approximately 400 K, which were approximately 70% of the values predicted for the fully ordered structure. The magnetic properties observed in the B 2-ordered films were well explained by ferrimagnetism that appeared in the B 2-ordered CoIrMnAl with full-swap disorders of Co-Ir and Mn-Al and almost full-swap disorder of Co-Mn, which was predicted from the first-principles calculations.

First principles calculations of 3d-4d transition metal based LiMgPdSn–type FeCrRuZ (Z = Al, Ga, In, Si) equiatomic quaternary Heusler alloys

We have investigated the structural, electronic and magnetic properties of the equiatomic quaternary Heusler (EQH) alloys FeCrRuZ (Z = Al, Ga, In, Si) using density functional theory. The structural study reveals that all the FeCrRuZ (Z = Al, Ga, In, Si) alloys stabilized to Y1 type structural configuration with ferrimagnetic ordering. The spin-polarized density of states (DOS) calculation demonstrates that FeCrRuAl alloy exhibits unusual spin-gapless half-metallic (SG-HM) behavior with majority spin-up channel possessing metallic characteristic and minority spin-down channel showing spin-gapless nature. The FeCrRuSi, FeCrRuGa and FeCrRuIn alloys display half-metallic, nearly half-metallic and metallic nature, respectively. The FeCrRuAl and FeCrRuSi alloys greatly follow the Slater-Pauling rule and give 100% spin-polarization at the Fermi level with total integer magnetic moment of 1 and 2 μB, respectively. In all, the total magnetic moment of FeCrRuZ (Z = Al, Ga, In, Si) alloys is contributed mainly by Cr atoms. The origin of the half-metallic band gap is elucidated through a schematic molecular orbital (MO) diagram. Further, the role of main group elements on structural, electronic, magnetic and half-metallic properties are explored in greater detail.

Determination of phase stability, half metallicity, mechanical and thermal behavior of Fe based quaternary Heusler alloys

Structural, magnetic, mechanical, and thermal characteristics of equiatomic quaternary Heusler alloys (EQHA) FeTiVZ (Z = Ga, In) and FeZrVZ (Z = Ga, In) were examined by employing full potential – linearized augmented plane wave (FP-LAPW) scheme. The calculations for structural optimization were performed for three different types of structures based on atomic positions named as Type I (TI), Type II (TII) and Type III (TIII). Geometry optimization results confirmed that TI is the most optimized structure as compared to other two types. The phase stability calculations confirmed the ferromagnetic (FM) nature of these Heusler alloys (HA). The magnetic characteristics have shown that the findings of band structures are agreed to the density of states (DOS). All these Fe-based HA have clear band gap (Eg) in spin down (S↓) channel which confirmed their half metallic (HM) nature and 100% spin polarization (SP). The S↓Eg of FeTiVGa, FeTiVIn, FeZrVGa, and FeZrVIn is 0.33eV, 0.35eV, 0.90eV, and 0.84eV respectively. The elastic constants and other calculated mechanical parameters verify the mechanical stability of compounds except FeTiVIn which needs further investigation. Based on elastic constants, the calculated Debye temperature (θD), and melting temperature (Tm) proves the thermodynamic stability of FeZrVZ (Z = Ga, In) and FeTiVGa. The obtained results have predicted that these alloys may be utilized in spintronic applications.

Density functional study of CoFeCrZ (Z=Al, Si, Ga, Ge) quaternary Heusler alloys for phonon spectra

Density Functional Theory (DFT) is used to investigate the phonon properties of CoFeCrZ (Z[Formula: see text]=[Formula: see text]Al, Si, Ga, Ge) equiatomic Quaternary Heusler Alloys. These alloys crystallize in face centered cubic (FCC) structure and have three crystal structures Y-Type I, Y-Type II and Y-Type III on the basis of their atomic positions. For CoFeCrZ (Z[Formula: see text]=[Formula: see text]Al, Si, Ga, Ge), Y-Type I is the most stable structure found in the literature, so phonon dispersion curves for this structure are obtained with the help of norm-conserving pseudo potentials in Quantum ESPRESSO. Absence of negative frequencies in phonon dispersion curves proves the dynamical stability of all these alloys. Phonon dispersion curves are further used to obtain Reststrahlen band, a region where light reflects 100%. The calculated Reststrahlen bands for CoFeCrAl, CoFeCrSi, CoFeCrGa and CoFeCrGe are 4.179 THz ([Formula: see text]m), 4.30 THz ([Formula: see text]m), 3.35 THz ([Formula: see text]m) and 3.05 THz ([Formula: see text]m), respectively. These obtained values of Reststrahlen bands for CoFeCrZ (Z[Formula: see text]=[Formula: see text]Al, Si, Ga, Ge) lie within the far infra-red (FIR) region, and can be used in sensing, imaging and optoelectronic devices.

Characterization of the Equiatomic Quaternary Heusler Alloy ZnCdRhMn: Structural, Electronic, and Magnetic Properties

In this manuscript, we study the structural, electronic, and magnetic properties of the equiatomic quaternary Heusler alloy ZnCdRhMn in the framework of the first-principle calculations and Monte Carlo simulations. In fact, we have investigated the structural, the magnetic, and the electronic properties of the Zn-based equiatomic quaternary Heusler alloy ZnCdRhMn using the ab initio method in the bases on the GGA approximation. On the other hand, the critical behavior of the equiatomic quaternary Heusler alloy ZnCdRhMn has been outlined by the Monte Carlo simulations. For this end, we apply the Metropolis algorithm. The objective of this work is to improve the competition between the austenitic and martensitic phases on the existence of magnetic and electronic properties of this alloy. The half-metallic behavior is only improved for the austenitic structure and 100% of spin polarization has been found. Moreover, a high curie temperature is found for this alloy for the austenitic phase. We can conclude that the austenitic structure of this alloy is useful for the spintronic device applications.

Investigations on Gilbert damping, electronic, magnetic and Curie temperature for equiatomic quaternary Heusler alloys CrScCoZ

Using first-principles calculations, we systematically study Gilbert damping, electronic, magnetic and Curie temperatures of CrScCoZ (Z = B, Al, Ga, In, Tl, Si, Ge, Sn, Pb) quaternary Heusler alloys. Thermodynamical stable is estimated by using formation energy and phase separation, and their elastic constants meet the mechanical stable conditions apart from CrScCoSi alloy. For all alloys, a small Gilbert damping parameters at ambient temperature imply their lower energy loss as spintronics materials. Electronic calculations show that the CrScCoZ have a half-metallic nature, and of which the total magnetic moments obey the Slater-Pauling rule, and the presence of disorder reduces their spin polarization. Analysis of orbital population and density of states confirms that the exchange splitting between eg and t2g states leads to the formation of gap. Based on the calculated sum of exchange interactions, we demonstrate that the Cr(A)-Cr(A) and Co(C)-Cr(A) exchanges play a leading role in interactions, thus determine the Curie temperatures. Curie temperatures in CrScCoZ alloys are evidently higher than room temperature. Overall, we think that CrScCoZ alloys are promising candidates in future spintronic applications.

Investigation of atomic disorder in half metallic equiatomic quaternary Heusler alloy CoFeCrSi

In order to study the atomic disorder on electronic structure equiatomic quaternary Heusler alloy CoFeCrSi, we simulated 6 kinds of swap disorders and 12 kinds of antisite disorders. By employing first principles calculations, our work revealed that ordered CoFeCrSi could maintain a half-metallicity and total magnetic moment of 3 μB when lattice constant ranges from 5.55 to 5.76 Å. Among various disorders, Fe-Cr swap disorder and Si(Cr) antisite disorder could form spontaneously owing to their negative formation energies. Among various swap disorders, only Co-Fe swap disordered structure can preserve half metallicity, and spin polarization higher than 95% also can exist in Co-Si, Cr-Si and Fe-Cr swap disordered structures. Besides, spin down energy gap can be preserved in all antisite disorders except Co(Cr), Co(Si) and Fe(Si). Therefore, CoFeCrSi possesses robust half-metallicity.

Structural, electronic, magnetic properties and critical behavior of the equiatomic quaternary Heusler alloy CoFeTiSn

In this article, we study the exchange coupling interactions of the equiatomic quaternary Heusler alloy CoFeTiSn, using the two methods: Monte Carlo simulations and the ab-initio method. In a first step, we use the ab-initio calculations to investigate the structural, the electronic and the magnetic properties of this alloy under the GGA method. The analysis of the energy dependence on the lattice parameter a (Å) of the equiatomic quaternary Heusler alloy CoFeTiSn, is discussed for different atomic configurations. The ferromagnetic configuration is found to be the more stable one, with an optimal lattice parameter value 6.00 Å. On the other hand, the electronic structure results show that the compound CoFeTiSn exhibits a half-metallic character and a spin polarization of 100% at the Fermi-level. The total magnetic moment of this alloy is found to be equal to 2.00 μB which follows the Slater Pauling rule. Our results support the half-metallic behavior of the studied material. In order to complete this study, we reported the dependence of the critical transition temperature as a function of the parameter α of the equiatomic quaternary Heusler alloy CoFeTiSn. We showed that the critical temperature increases almost linearly with an increase of the values of the parameter α.

Investigation of the physical properties of the equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge): a DFT study

In this manuscript, we investigate the physical properties such as the magnetic and the electronic properties of the Co-based equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge). These investigations have been performed by employing the Quantum Espresso code in the framework of density functional theory (DFT). The generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) is used for all these calculations. The band structures, and density of states calculations, show that all these materials CoYCrZ (Z = Si and Ge) exhibit a half-metallic (HM) behavior only for the structure type II. Moreover, this structure type II is found to be the most stable configuration for all these alloys. On the other hand, it has been found that the Slater–Pauling is well described for the compound CoYCrGe, only for the configuration type II. In particular, the equiatomic quaternary Heusler alloys CoYCrSi and CoYCrGe are found to be half-metallic for the structure type II. This is due to the fact that they have 100% spin polarization SP. Also, the existence of complete SP in the studied alloys is the reason for which these materials are useful for spintronic device applications.

Search for half-metallicity in new ferrimagnetic quaternary MnXMoAl (X= Co and Ti) Heusler alloys: A DFT based investigation

Highly spin-polarized magnetic materials emerge as promising candidates for spintronic technology. Herein, we present a theoretical study of two new equiatomic quaternary Heusler alloys MnCoMoAl (MCMA) and MnTiMoAl (MTMA) in LiMgPdSn-type structure. On performing volume optimization in three possible Y-type structures, it is confirmed that the MCMA (MTMA) alloy is stable in Y1 (Y2)-type structure. The magnetic moment data reveals that alloys are ferrimagnetic (FIM) in the ground state. It is shown that MCMA is a highly spin-polarized (88.24%) metal, whereas, MTMA exhibits complete half-metallic properties with 100% spin-polarization and a band gap of about 0.20 eV in the spin-down channel at the Fermi level. Besides, MCMA carries a total magnetic moment of 0.92 μB whereas MCMA has an integral spin magnetic moment of ~2.0 μB. It is found that the largest moment is contributed by Co (Mn) atoms in MCMA (MTMA). To examine the effect of uniform strain on the magnetic properties, the total moment is calculated as a function of strain. It is noticed that the total moment of the alloys does not change significantly when strain is applied in the range −12%–12%. In addition, the effect of temperature and pressure on the thermodynamic properties has been examined. The coefficient of thermal expansion (α) and specific heat capacity (CV) increase (decrease) with increasing temperature (pressure). The Gru¨neisen parameter and Debye temperature remain almost unchanged when temperature varies from 0 K to 900 K. The proposed materials may have applications in future spintronics.

Half-metallic ferromagnetism and Ru-induced localization in quaternary Heusler alloy CoRuMnSi

We report a combined theoretical and experimental investigation of half-metallic ferromagnetism in equiatomic quaternary Heusler alloy CoRuMnSi. Room temperature XRD analysis reveals that the alloy crystallizes in L21 disordered structure instead of pristine Y-type structure due to 50% swap disorder between the tetrahedral sites, i.e., Co and Ru atoms. Magnetization measurements reveal a net magnetization of nearly 4 μB with Curie temperature, TC of ∼780 K. Resistivity measurement reveals the presence of localization effect below 35 K while above 100 K, a linear dependence is observed. The majority spin band near the Fermi level clearly indicates the overlap of flat eg bands with sharply varying conduction bands that are responsible for the localization. In-depth analysis of the projected atomic d-orbital character of band structure reveals unusual bonding, giving rise to the flat eg bands purely arising out of Ru ions. Co-Ru swap disorder calculations indicate the robustness of half-metallic nature, even when the structure changes from Y-type to L21-type, with no major change in the net magnetization of the system. Thus, high TC, robust stability, and half-metallic nature make this alloy a promising candidate for further exploration from the point of view of applied spintronics.

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).