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Unraveling the abnormal dependence of phase stability on valence electron concentration in Ni–Mn-based metamagnetic shape memory alloys.
- Source :
- Journal of Applied Physics; 7/28/2020, Vol. 128 Issue 4, p1-8, 8p, 1 Diagram, 2 Charts, 6 Graphs
- Publication Year :
- 2020
-
Abstract
- Valence electron concentration (e/a) dependence of phase transition temperature T<subscript>M</subscript>, i.e., a higher e/a leading to an elevated T<subscript>M</subscript>, is a well-accepted criterion for the Ni–Mn-based alloys. However, this tendency is not always obeyed by certain alloy systems, such as the Ni<subscript>2</subscript>Mn(Ga, Z) alloys (Z = Si, Ge, and Sn). The origin of this abnormal behavior remains uncovered. In this work, by first-principles calculations, the origin of the abnormal e/a dependence of phase stability in the Ni<subscript>2</subscript>MnGa<subscript>1−x</subscript>Si<subscript>x</subscript> (x = 0–1) alloys is elucidated through examining the electronic structure, phonon, and magnetism. We find that the abnormal e/a dependence of phase stability intrinsically originated from the chemical composition change. The composition variation brings about a reduction of the minority-spin electronic states near the Fermi energy and the weakness of the Fermi surface nesting. Moreover, the substitution of Si for Ga leads to a decreased magnetization of austenite and an increased magnetization of martensite, which also makes a non-negligible contribution to the abnormal phase stability. The conclusions drawn for the Ni<subscript>2</subscript>MnGa<subscript>1−x</subscript>Si<subscript>x</subscript> alloys can be well extended to understand the structural transition in other abnormal alloying systems, such as the Ni<subscript>2</subscript>MnGa<subscript>1−x</subscript>Z<subscript>x</subscript> alloys (Z = Ge and Sn). This work clarifies the origin of the abnormal dependence of phase stability on e/a in the Ni–Mn-based alloys and provides solid knowledge for the design of advanced magnetic shape memory alloys. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00218979
- Volume :
- 128
- Issue :
- 4
- Database :
- Complementary Index
- Journal :
- Journal of Applied Physics
- Publication Type :
- Academic Journal
- Accession number :
- 144934586
- Full Text :
- https://doi.org/10.1063/5.0009638