Half-Metallic Ferrimagnetic Characteristics of Co2YZ (Z = P, As, Sb, and Bi) New Full-Heusler Alloys: a DFT Study

The full-Heusler alloys Co(2)YZ (Z = P, As, Sb, and Bi) were investigated by using the state-of-the-art full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method within the framework of density functional theory (DFT), to understand the structural, electronic, and magnetic properties of these new Heusler alloys. The generalized gradient approximation (GGA) was chosen to define the exchange-correlation potential for studying the structural properties, whereas electronic and magnetic properties were developed by using the GGA + U scheme, where U is the Hubbard term, which explains the Coulomb repulsion and was applied to describe the "d" electrons. The structural properties indicated that the ferromagnetic states of these compounds are energetically more favorable than the paramagnetic states. Through results on the electronic structures (band structures and densities of states), it is found that all these alloys exhibit a complete half-metallic nature, with half-metallic gaps (E-HM) of 0.632, 0.605, 1.223, and 0.922 eV for Co2YP, Co2YAs, Co2YSb, and Co2YBi alloys, respectively. The magnetic properties indicated that the total spin magnetic moments of these Heusler alloys obey the Slater-Pauling rule around value 2 A mu (B) approximately. The local magnetic moments of Co and Y transition elements have opposite signs with different intensities, thus revealing the ferromagnetic character. Our study of both electronic and magnetic properties demonstrates in detail that Co(2)YZ (Z = P, As, Sb, and Bi) full-Heusler alloys are complete half-metallic ferrimagnetic materials.