Tunability of Structure and Magnetism in Heusler Mn<SUB>3-x</SUB>Co<SUB>x</SUB>Ga (0 ≤ x ≤ 1)

다국어 초록 (Multilingual Abstract)

Mn₃Ga has drawn interest in spintronics for potential applications due to large perpendicular magnetic anisotropy, high Curie temperature (~760 K), and low magnetization. Motivated by previous studies on tunability of magnetism through transition metal substitutions in Mn₃Ga, we investigate magnetic and structural properties of Mn₃Ga upon Co substitution using first-principles calculations. In the absence of Co, Mn₃Ga is in tetragonal phase. With Co, both tetragonal and cubic phases occur. x ≤ 0.5, tetragonal phase is preferred, while x > 0.5, cubic one is favored. Co magnetic moment in two phases exhibit different magnetic behaviors. In tetragonal phase, unlike other Co compounds, Co magnetic moment nearly vanishes. On the other hand, in cubic phase, it retains a usual moment at about 1 μB. Nearly vanishing Co magnetic moment in tetragonal structure is elucidated phenomenologically by the magnetic exchange coefficient, where coupling between Co and Mn is much smaller than cubic one. Furthermore, anomalous Hall conductivities (AHC) are investigated for x = 0, 0.5, and 1. The magnitude of AHC is about 100~500 S/cm, where the sign change occurs at 0.5 < x < 1.