Mn2CoZ(Z=Al,Ga,

Abstract

We study the electronic structures and magnetic properties of Mn 2 CoZ ͑Z =Al,Ga,In,Si,Ge,Sn,Sb͒ compounds with Hg 2 CuTi-type structure using first-principles full-potential linearized-augmented plane-wave calculations. It is found that the compounds with Z = Al, Si, Ge, Sn, and Sb are half-metallic ferrimagnet. Experimentally, we successfully synthesized the Mn 2 CoZ ͑Z =Al,Ga,In,Ge,Sn,Sb͒ compounds. Using the x-ray diffraction method and Rietveld refinement, we confirm that these compounds form Hg 2 CuTi-type structure instead of the conventional L2 1 structure. Based on the analysis on the electronic structures, we find that there are two mechanisms to induce the minority-spin band gap near the Fermi level, but only the d-d band gap determines the final width of the band gap. The magnetic interaction is quite complex in these alloys. It is the hybridization between the Mn͑C͒ and Co atom that dominates the magnitude of magnetic moment of the Co atom and the sign of the Mn͑B͒-Co exchange interaction. The Mn 2 CoZ alloys follow the Slater-Pauling rule M H = N V − 24 with varying Z atom. It was further elucidated that the molecular magnetic moment M H increases with increasing valence concentration only by decreasing the antiparallel magnetic moment of Mn͑C͒, while the magnetic moments of Mn͑B͒ and Co are unaffected.

Ab Initio Investigation of Half-Metallic Behaviour in the Full-Heusler X2MnGe (X = Sc, Fe, Ni)

“…6 for Sc 2 MnGe in CuHg 2 Ti-type structure, the presence of the minority spin states at the Fermi level and a wide band gap in the majority spin state confirm HM characteristic; similar results were observed for Sc 2 MnZ (Z = C, Si, Ge, and Sn) [29] It can be seen in Fig. 6 for Sc 2 MnGe that the energy regions from −5 to 0 eV consist mainly of electrons of Sc (A), Sc (B [34][35][36]. The covalent band gap has been found to exist in half-Heusler alloys with C1 b structure.…”

First-Principles Study of Magnetism and Half-Metallic Properties for the Quaternary Heusler Alloys CoMnTiZ (Z = P, As, and Sb)

“…Heusler alloys have the structural formulas of X 2 YZ with L2 1 structure and XYZ with C 1b structure, where X and Y are transition metals and Z is a main-group element. There are some theoretical studies which predicted HM characteristic in Heusler compounds mainly in Co 2 -based alloys with L2 1 structure [25][26][27][28][29][30][31].…”

First-Principles Study of Structural, Electronic, Magnetic and Half-Metallic Properties of the Heusler Alloys Ti2ZAl (Z = Co, Fe, Mn)

“…The minority-spin band gap is an important factor in HM materials, and the cause of the HM band gap is discussed in the following. The HM band gaps usually take place from three aspects [24]: (1) covalent band gap which exists in the half-Heusler with C 1b structure, (2) d-d band gap that is the origin of the HM band gap in the full-Heusler alloys with AlCu 2 Mn structure and (3) charge transfer band gap [24,25] which is usually seen in CrO 2 and double perovskites [24,26]. The origin of the band gap in Fe 2 CrSi for example has been discussed by Galanakis et al [27], who related the band gap to the covalent hybridization between the lower d bands of the high-valent transition metal (Fe) with the higher d bands of the lower-valent transition metal (Cr).…”