Lattice Dynamics, Mechanical Properties, Electronic Structure and Magnetic Properties of Equiatomic Quaternary Heusler Alloys CrTiCoZ (Z = Al, Si) Using First Principles Calculations

Abstract

First principles calculations are performed to investigate the thermodynamical stability, dynamical, mechanical, electronic and magnetic properties of CrTiCoZ (Z = Al/Si) novel quaternary Heusler alloys. A Y-type III atomic configuration is found to be the most stable structure for both compounds. The lattice constant values obtained using GGA-PBE approach are 5.9368 Å and 5.7853 Å for CrTiCoAl and CrTiCoSi, respectively. Using the value of elastic moduli for both the compounds, the computed Pugh’s ratio value is 2.5 and 2.7 for CrTiCoAl and CrTiCoSi, respectively, which is higher than 1.75, indicating both the compounds are ductile in nature. The melting temperatures of both compounds are as high as 2142 K and 2420 K for CrTiCoAl and CrTiCoSi, respectively. The electronic structure calculations, using the GGA-PBE approach, show a half metallic behavior of CrTiCoAl. The spin-down channel exhibits a direct band gap of 0.15 eV, whereas the spin-up channel is metallic, making CrTiCoAl a half metallic ferromagnet with 100% spin polarization and an appreciable magnetic moment of −2 µB. However, CrTiCoSi is found to be semi-metallic in the spin-down channel and metallic in the spin-up channel, which leads to a spin polarization of 99.7% with a non-integer magnetic moment of −0.99 µB. The Curie temperature of CrTiCoAl is well above the room temperature (385 K), whereas that of CrTiCoSi is below the room temperature (203 K). Thus, CrTiCoAl is found to be more promising than CrTiCoSi as a spin injector in spintronic devices.