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ZELENÝ, M. SOZINOV, A. BJÖRKMAN, T. STRAKA, L. NIEMINEN, R.
Original Title
Ab initio study of Co- and Cu-doped Ni-Mn-Ga alloys
Type
abstract
Language
English
Original Abstract
Much attention has been paid to the Ni-Mn-Ga magnetic shape memory (MSM) alloy because it exhibits interesting properties such as a giant magnetic field-induced strain (MFIS). The MFIS occur below the martensitic transformation temperature, when a high-temperature cubic phase, austenite, transforms to a phase with lower symmetry, martensite. The martensitic transformation point can be adjusted by doping. The MFIS of 12% has recently been reported in the nonmodulated martensite with reduced c/a, achieved by simultaneous doping by 4% of Cu and Co. The influence of Co and Cu doping on Ni-Mn-Ga is investigated using the exact mufin-tin orbital method in combination with the coherent-potential approximation. Single element doping and simultaneous doping by both elements are studied in Ni50−xCoxMn25−yGa25−zCuy+z alloys. Doping with Co in the Ni sublattice decreases the c/a ratio of the nonmodulated martensite but it simultaneously increases the cubic phase stability. Doping with Cu in the Mn or in Ga sublattices does not change c/a ratio significantly and it decreases the cubic phase stability. For combined simultaneous doping by Co and Cu sublattices the effects of the individual dopants are independent and about the same as for the single element doping. The described effects can be understood on the basis of a density of states analysis, by studying the states that drive the Jahn-Teller instability that gives rise to the martensitic transformation.
Keywords
shape memory alloys; Ni2MnGa; doping; ab initio
Authors
ZELENÝ, M.; SOZINOV, A.; BJÖRKMAN, T.; STRAKA, L.; NIEMINEN, R.
Released
26. 2. 2014
Publisher
ViCoM
Location
Vienna
Pages from
35
Pages to
Pages count
1
BibTex
@misc{BUT108087, author="Martin {Zelený} and Alexei {Sozinov} and Torbjörn {Björkman} and Ladislav {Straka} and Risto M. {Nieminen}", title="Ab initio study of Co- and Cu-doped Ni-Mn-Ga alloys", booktitle="From Electrons to Phase Transitions", year="2014", pages="35--35", publisher="ViCoM", address="Vienna", note="abstract" }