Indagine DFT sulle Proprietà Termiche e Deviazioni dalla Stechiometria nelle Leghe Heusler a Base di Co

With the current development of spintronic devices, there is a growing interest in half-metallic ferromagnets due to their ability to conduct spin-polarized current. Co-based Heusler alloys, such as Co2HfSn and Co2ZrSn, are among the promising materials as they exhibit good thermal stability, combined with suitable magnetic and transport properties. However, experimental results have shown that these alloys can have off-stoichiometric compositions. Therefore, the electronic structure and the effects of deviations from ideal stoichiometry on the magnetism and half-metallicity of these alloys are analyzed using ab initio calculations within the density functional theory (DFT) framework. Furthermore, their phonon-related thermal properties have never been studied. In this work, the thermal properties of Co2HfSn and Co2ZrSn are also analyzed using the finite displacement method. The phonon density of states and band structure have been calculated within the harmonic approximations. The nonexistence of imaginary phonon frequencies ensures their dynamical stability. From the phonon frequencies, the thermal properties of Helmholtz free energy, entropy, and heat capacity at constant volume as a function of temperature are evaluated. These outcomes will offer new perspectives for the implementation and development of Co-based Heusler alloys in spintronic applications.