Study of half metallicity, structural and mechanical properties in inverse Heusler alloy Mn2ZnSi(1-x)Ge x and a superlattice

Investigation of mechanical, thermodynamical, dynamical and electronic properties of RuYAs (YCr and Fe) alloys

Investigation of structural, dynamical, mechanical, electronic and thermodynamic properties of RuYAs (Y= Cr and Fe) alloys have been performed from the first principle calculations. Among the three structural phases, 'α' phase is found to be energetically favorable for both the RuCrAs and RuFeAs compounds. The computed cohesive energies and phonon dispersion spectra indicate the structural and dynamical stabilities of both the compounds. Mechanical stability of these compounds are studied using elastic constants. The Pugh's ratio predicts RuFeAs to be more ductile than RuCrAs. The RuCrAs alloy, on the other hand, is found to be a stiffer, harder and highly rigid crystal with stronger bonding forces than the RuFeAs. Furthermore, the thermodynamical properties have also been estimated with respect to the temperature under different pressures using the quasi-harmonic Debye model. In order to account for the effect of the highly correlateddtransition elements in the system we incorporated the GGA +Uapproximations. Within the GGA +Uapproach, the electronic structure reveals the half-metallicity for both compounds, which follows the Slater-Pauling rule. The charge density and electron localized function reflect the covalent bonding among the constituent atoms. Bader analysis reveals that the charge transfer takes place from Cr/Fe to Ru and As atoms in both approximations. Both Raman and infrared active modes have been identified in the compounds.

Effects of Interfacial Termination, Oxidation, and Film Thickness on the Magnetic Anisotropy in Mn2.25Co0.75Ga0.5Sn0.5/MgO Heterostructures

Perpendicular magnetic anisotropy (PMA) is a determining factor for the realization of nonvolatile information storage devices with high efficiency and thermal stability. In this work, a new spin gapless semiconductor Mn_2.25Co_0.75Ga_0.5Sn_0.5 Heusler alloy with an inter-spin zero gap was first designed theoretically. The Mn_2.25Co_0.75Ga_0.5Sn_0.5 bulk was prepared successfully in experiment. The effects of interfacial termination, oxidation, and film thickness on the magnetic anisotropy of Mn_2.25Co_0.75Ga_0.5Sn_0.5/MgO (MCGS/MgO) heterostructures are investigated systematically by first-principles calculations. The results show that all the Mn(A)Mn(C)GaSn-, Mn(A)Mn(C)CoGaSn-, Mn(B)GaSn_I-, and Mn(B)GaSn_II-terminated MCGS/MgO heterostructures (called as AC1, AC2, BD1, and BD2 models, respectively) present PMA, which mainly derives from the interfacial and surficial MCGS layers. Furthermore, the PMA of MCGS/MgO heterostructures can be preserved in a large range of interfacial oxidization (up to ±50%). With MCGS thickness increasing from 5 to 16 monolayers, the PMA of MCGS/MgO heterostructures with an AC-type surface decreases significantly. However, the PMA of BD-type surface models is relatively robust to the thickness of the MCGS layer, and the magnetic anisotropy always points to the out-of-plane direction. Therefore, MCGS Heusler alloy is a new promising spin gapless semiconductor candidate for spintronics applications. The robust and tunable PMA in MCGS/MgO heterostructures offers the possibility for developing nonvolatile data memory devices.

Highly spin-polarized electronic structure and magnetic properties of Mn2.25Co0.75Al1−xGex Heusler alloys: first-principles calculations

Highly spin-polarized half-metals (HMs) and spin-gapless semiconductors (SGSs) are the promising candidates in spintronic devices. However, the HM and SGS Heusler materials are very sensitive to the stoichiometric defects and lattice distortion, which will be not beneficial to the practical applications. Here, the electronic structure and magnetic properties of Mn_2.25Co_0.75Al_1−xGe_x (x = 0, 0.25, 0.50, 0.75 and 1.00) Heusler alloys were investigated by first-principles calculations. Large negative formation energy, cohesive energy and phonon spectra confirm that the Mn_2.25Co_0.75Al_1−xGe_x alloys are stable. It is found that Mn_2.25Co_0.75Al_1−xGe_x with x = 0, 0.25, 0.75 and 1.00 show robust ferrimagnetic HM characteristics, while Mn_2.25Co_0.75Al_0.5Ge_0.5 shows robust SGS characteristic. Under the hydrostatic and uniaxial strains, Mn_2.25Co_0.75Al_1−xGe_x exhibit a series of rich electronic transitions. The magnetic anisotropy of Mn_2.25Co_0.75Al_1−xGe_x turns from the in-plane [100] direction to the out-of-plane [001] one by applying the uniaxial strains. The results suggest that the complete spin polarizations of Mn_2.25Co_0.75Al_1−xGe_x alloys are robust against the stoichiometric defects and lattice distortion, which have potential applications in spintronic devices.

The complete spin polarizations of Mn_2.25Co_0.75Al_1−xGe_x are proved to be robust against stoichiometric defect and lattice deformation, whose easy magnetization direction can be manipulated from in-plane direction to out-of-plane one under uniaxial strain.