Influence of Co and Mn substitution on magnetic properties of novel Y2FeSi Heusler alloy

This paper presents results of density functional theory (DFT) studies on structural, electronic, and magnetic properties of novel Y2FeSi Heusler material characterized by spin polarization at Fermi level of [Formula: see text] and magnetic moment of 1.56 [Formula: see text]. The total magnetic moment of investigated material is dominated by Iron sites, while magnetic moments coming from Yttrium sites are aligned antiparallel to the Iron. Here, we introduced Co and Mn substitutions to alter the magnetic and electronic properties of the studied material. The Heusler alloys are very sensitive to electronic structure changes induced by ionic substitutions, which allowing to specifically modulate their properties. The Co-substitution lowered the total magnetic moment to [Formula: see text][Formula: see text]1.20 [Formula: see text] and Mn caused a rise to [Formula: see text][Formula: see text]1.93 [Formula: see text]. Introduction of Mn resulted in [Formula: see text] spin polarization. We hope that this study will promote further theoretical as well as experimental interest in these types of compounds.

Thermoelectric and Half-Metallic Behavior of the Novel Heusler Alloy RbCrC: Ab initio DFT Study

Research Highlights • Electronic, magnetic, elastic and thermoelectric properties of RbCrC alloy are investigated. • Material is half-metallic, ductile and anisotropic in nature. • The total magnetic moment (3[Formula: see text][Formula: see text]B) obeys the Slater–Pauling rule. • The HM RbCrC compound is identified as potential candidate for spintronic applications. • ZT calculated values of 0.89 and 0.94 make RbCrC a promising thermoelectric material candidate for use in future devices. The aim of this work is to investigate the half-metallicity behavior, elastic, thermodynamic and thermoelectric (TE) properties of the Heusler compound RbCrC using the generalized gradient approximation (GGA-PBE96) and the modified Becke–Johnson (mBJ) approach. The electronic band structures and density of states reveal that RbCrC is a half-metallic ferromagnet (HMF). The calculated total magnetic moment of 3[Formula: see text][Formula: see text]B follows the Slater–Pauling rule ([Formula: see text]). The half-metallicity character can be maintained in the 5.4–7.4 Å lattice constants range and the 0.8–1.2 [Formula: see text]/[Formula: see text] ratio range. Existence of half-metallic ferromagnetism in RbCrC makes it a promising material for practical applications in the spintronic field. Also, the RbCrC exhibits a ductile and anisotropic behavior. The quasi-harmonic Debye model (QHDM) is used to calculate the thermodynamic properties. The BoltzTraP code which is based on semi-classical Boltzmann theory (SCBT) is applied for calculating TE properties. According to the obtained figure of merit values (ZT between 0.89 and 0.94 from 50 K to 800 K), the RbCrC alloy remains a good candidate for thermoelectric applications.

DFT Investigation on the Electronic, Magnetic, Mechanical Properties and Strain Effects of the Quaternary Compound Cu2FeSnS4

The electronic, magnetic and mechanical properties of the quaternary compound Cu2FeSnS4 have been investigated with first principle calculations. Its half-metallicity has been identified with spin polarized band structures and its magnetic origination is caused by the strong spin splitting effect in the d orbitals of Fe atoms. The total magnetic moment of 4 μB is mainly contributed by the Fe atoms and the spatial distribution of the magnetic spin density and charge density difference have also been examined. Moreover, several mechanical properties of Cu2FeSnS4 have been derived and its mechanical stability is also verified. The directional dependent Young’s modulus exhibits relatively small anisotropy yet the shear modulus shows strong directional anisotropy. At last, the tetragonal strain effects have been evaluated and their impact on the electronic and magnetic properties are provided. Results show the total magnetic moment stays almost unchanged while the half-metallicity can only be maintained under relatively small variations for both strains. This study can provide comprehensive information about the various properties of Cu2FeSnS4 compound and serve as a helpful reference for its future applications.

Theoretical Study of the Electronic, Magnetic, Mechanical and Thermodynamic Properties of the Spin Gapless Semiconductor CoFeMnSi

CoFeMnSi has been both experimentally and theoretically proven as a novel spin-gapless semiconductor and resulted in a new research direction in equiatomic full Heusler compounds. Using the first-principles calculation method, we investigated the electronic, magnetic and mechanical properties of CoFeMnSi material in this study. The obtained lattice constant under the LiMgPdSn-type Heusler structure is 5.611 Å and it is fairly consistent with previous experimental results and theoretical calculations. Furthermore, the achieved total magnetic moment of 4 μB follows the Slater–Pauling rule as Mtotal = Ztotal − 24, where Mtotal is the total magnetic moment per formula unit and Ztotal is the total valence electron number, i.e., 28 for CoFeMnSi material. We have also examined the mechanical properties of CoFeMnSi and computed its elastic constants and various moduli. Results show CoFeMnSi behaves in a ductile fashion and its strong elastic anisotropy is revealed with the help of the 3D-directional-dependent Young’s and shear moduli. Both mechanical and dynamic stabilities of CoFeMnSi are verified. In addition, strain effects on the electronic and magnetic properties of CoFeMnSi have been investigated, including both uniform and tetragonal strains, and we found that the spin-gapless feature is easily destroyed with both strain conditions, yet the total magnetic moment maintains a good stability. Furthermore, the specific behaviors under various temperatures and pressures have been accessed by the thermodynamic properties with a quasi-harmonic Debye model, including bulk modulus, thermal expansion coefficient, Grüneisen constant, heat capacity and Debye temperature. This comprehensive study can offer a very helpful and valuable reference for other relative research works.

Theoretical Study of the Electronic and Magnetic Properties and Phase Stability of the Full Heusler Compound Pd2CoAl

Based on first principles calculation, a systematical investigation has been performed to study the electronic, magnetic, dynamic, and mechanical properties of the full Heusler compound Pd2CoAl. It is found that the L21-type structure is energetically more stable than the XA-type due to the lower total energy. The obtained lattice constant in cubic ground state is 6.057 Å, which matches well with previous study. The calculated electronic band structure reveals the metallic nature of Pd2CoAl and its total magnetic moment of 1.78 μB is mainly contributed by Co atom from strong spin splitting effect, as indicated with the distinctive distributions of the density of states in two spin directions. Under uniform strains from −5% to +5%, the variation of total magnetic moment has been obtained and it is still caused by the much larger change from Co atom, compared with Pd and Al atoms. The tetragonal structure has further been analyzed and we found that there is possible martensitic phase transformation because the total energy can be further reduced when the cubic structure is varied into the tetragonal one. The large energy difference of 0.165 eV between the tetragonal and cubic phases is found at the c/a ratio of 1.30. The total density of states has been compared between the cubic and tetragonal phases for Pd2CoAl and results show tetragonal phase transformation could reduce the states at the Fermi energy level in both directions. In addition, the dynamic and mechanical stabilities have also been evaluated for Pd2CoAl in both cubic and tetragonal structures and results confirm that the tetragonal phase shows good stability against the cubic phase, which further verifies that the tetragonal phase transformation is highly expected. In the end, the strong elastic anisotropy in the tetragonal structure has been clearly shown with the calculated directional dependence of the Young’s modulus and shear modulus.

Theoretical Investigations on the Mechanical, Magneto-Electronic Properties and Half-Metallic Characteristics of ZrRhTiZ (Z = Al, Ga) Quaternary Heusler Compounds

The electronic, magnetic, and mechanical properties were investigated for ZrRhTiZ (Z = Al, Ga) quaternary Heusler compounds by employing first-principles calculations framed fundamentally within density functional theory (DFT). The obtained electronic structures revealed that both compounds have half-metallic characteristics by showing 100% spin polarization near the Fermi level. The half-metallicity is robust to the tetragonal distortion and uniform strain of the lattice. The total magnetic moment is 2 μB per formula unit and obeys the Slater-Pauling rule, Mt = Zt − 18 (Mt and Zt represent for the total magnetic moment and the number of total valence electrons in per unit cell, respectively). The elastic constants, formation energy, and cohesive energy were also theoretically calculated to help understand the possibility of experimental synthesis and the mechanical properties of these two compounds.

Unraveling the effect of B-site antisite defects on the electronic and magnetic properties of the quadruple perovskite CaCu3Fe2Nb2O12

The total magnetic moment of the quadruple perovskite CaCu3Fe2Nb2O12 is significantly reduced owing to the B-site antisite defects. They not only introduce the Fe(↓)–O–FeNb(↑) antiferromagnetic arrangement, but also induce antiparallel Cu spins in the totally disordered CaCu3Fe2Nb2O12.

Spin Gapless Semiconductor–Nonmagnetic Semiconductor Transitions in Fe-Doped Ti2CoSi: First-Principle Calculations

Employing first-principle calculations, we investigated the influence of the impurity, Fe atom, on magnetism and electronic structures of Heusler compound Ti2CoSi, which is a spin gapless semiconductor (SGS). When the impurity, Fe atom, intervened, Ti2CoSi lost its SGS property. As TiA atoms (which locate at (0, 0, 0) site) are completely occupied by Fe, the compound converts to half-metallic ferromagnet (HMF) TiFeCoSi. During this SGS→HMF transition, the total magnetic moment linearly decreases as Fe concentration increases, following the Slate–Pauling rule well. When all Co atoms are substituted by Fe, the compound converts to nonmagnetic semiconductor Fe2TiSi. During this HMF→nonmagnetic semiconductor transition, when Fe concentration y ranges from y = 0.125 to y = 0.625, the magnetic moment of Fe atom is positive and linearly decreases, while those of impurity Fe and TiB (which locate at (0.25, 0.25, 0.25) site) are negative and linearly increase. When the impurity Fe concentration reaches up to y = 1, the magnetic moments of Ti, Fe, and Si return to zero, and the compound is a nonmagnetic semiconductor.