J Supercond Nov Magn DOI 10.1007/s10948-017-4299-7 ORIGINAL PAPER Density Functional Study of Half-Metallic Ferromagnetism in the New Heusler Compounds CaYO 2 (Y = Sc, Ti,V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) S. Hosseini 1 · F. Ahmadian 1 Received: 5 August 2017 / Accepted: 11 August 2017 © Springer Science+Business Media, LLC 2017 Abstract The structural, electronic, and magnetic proper- ties of full-Heusler alloys CaYO 2 (Y = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) were investigated using full- potential linearized augmented plane wave method based on density functional theory. It was confirmed that these compounds can be synthesized experimentally due to their negative formation energies. The results predicted that all compounds in AlCu 2 Mn-type structure were more stable than CuHg 2 Ti-type structure. The band structure calcula- tions showed that alloys CaYO 2 (Y = Cr, Fe, Ni, and Cu) in AlCu 2 Mn-type structure and CaYO 2 (Y = Ti, V, Cr, Co, and Ni) in CuHg 2 Ti-type structure have half metallic behavior. The origin of half-metallic characteris- tic was investigated using electronic density of states for CaFeO 2 . Among these alloys, CaCrO 2 was half-metal in a wide range of lattice constants indicating its resistance against destructive factors of half-metallicity such as tem- perature and pressure. The total magnetic moments for half- metallic alloys were integer values and obeyed the Slater- Pauling rules. The CaYO 2 alloys with half-metallic char- acter may be good candidates for practical applications in spintronics. Keywords Half-metals · Heusler alloys · Magnetic properties · Electronic properties  F. Ahmadian ahmadian@iaush.ac.ir 1 Department of Physics, Shahreza Branch, Islamic Azad University, Shahreza, Iran 1 Introduction In the last decade, due to the increasing interest in the field of spintronics, several researches on the so-called half-metallic (HM) materials have been performed. HM materials have a metallic characteristic for one spin direc- tion and are semiconducting for the other spin direction at the same time exhibiting a 100% spin polarization at the Fermi level [1–3]. Half-metallicity was first predicted by de Groot and collaborators in NiMnSb half-Heusler alloy [4]. Since then, half-metallicity has been widely ver- ified in Heusler alloys [5–20], ferromagnetic oxides [21, 22], perovskite compounds [23–25] and some diluted mag- netic semiconductors (DMS) [26–29]. Heusler alloys are particularly attractive because of their higher Curie tempera- tures than other HM materials and their structural similarity to the widely used binary semiconductors like GaAs and InP [30, 31]. Up to now, half-metallicity in many Heusler alloys has been predicted using the electronic structure calculations based on first-principle methods. Most of the predicted HM Heusler alloys include transition metals such as Co 2 -, Fe 2 -, Cr 2 -, V 2 -, Ti 2 -, and Sc 2 -based alloys [8, 32–44]. Recently, several studies have been performed on full- Heusler or half-Heusler structures excluding transition met- als such as GeKCa and SnKCa [45], XNaCa (X = C and Si) [46], RbSrX(X = C, Si, and Ge), and XCsSr (X = C, Si, Ge, and Sn) [47, 48], KCaX 2 (X = C, N, and O) [49], RbSrX 2 (X = C, N, and O) [50], and CsBaX 2 (X = C, N, and O) [51]. These alloys are known as sp or d 0 half-metals and due to their small magnetic moments, lower stray fields, and energy loss, they are preferable in spintronic device applications.