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Effect of Co substitution on ferrimagnetic Heusler compound Mn3Ga
Nguyen Quynh Anh T.,Ho Thi H.,Jung Myung-Hwa,Rhim Sonny H. 한국물리학회 2023 Current Applied Physics Vol.49 No.-
Effect of Co substitution on Mn3Ga is investigated using first-principles study for structural and magnetic properties. Without Co, ferrimagnetic Heusler compound Mn3Ga is in tetragonal phase. With Co substitution, depending on Co concentration (x), Mn3Ga prefers tetragonal (cubic) phase when x ≤ 0.5 ( x ≥ 0.5). Ferrimagnetism is robust regardless of x in both phases. While magnetic moments of two Mn do not vary significantly with x, magnetic moments of Co in two phases exhibit different behaviors, leading to distinct features in absolute value of total magnetic moment (|Mtot |). When x ≤ 0.5, in tetragonal phase, magnetic moment of Co is vanishingly small, resulting in a decrease of |Mtot | with x. In contrast, when x ≥ 0.5, in cubic phase, magnetic moment of Co is roughly 1μB, which is responsible for the increase of |Mtot |. Electronic structure is analyzed with partial density of states for various x. To elucidate the counterintuitively small Co moment, the magnetic exchange interaction is investigated, where exchange coefficient between Co and Mn(II) in x ≤ 0.5 is much smaller than that in x ≥ 0.5.
Spin Hall Conductivities of W-N Alloys
Quynh Anh T. Nguyen,D. D. Cuong,S. C. Hong,Sonny H. Rhim 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
Motivated by recent reports on high spin Hall angle in W alloys [1-3], spin Hall conductivities (SHC) of W-N alloys are investigated theoretically using ab initio density functional calculations. Without N, SHC of α-W and β-W are -744 and 818 ℏ/S/cm, respectively. Among various combinations, we focus on W<sub>2</sub>N and WN. In particular, SHC of W<sub>2</sub>N is enhanced 18.7 % over β-W. High SHC of W<sub>2</sub>N is elucidated by large Berry curvature from 2/3rx. On the other hand, in WN case, three structures, NaCl-type, hexagonal and NbO-type, are considered. SHC of NaCl- and hexagonal types are -619 and –696 ℏ/S/cm, respectively, while NbO-type exhibits relatively low SHC of –194 ℏ/S/cm. However, considering energetics, W<sub>2</sub>N is more promising than WN, whose thermodynamic average is around –194 ℏ/S/cm.