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Title: Ferromagnetic shape memory in the NiMnGa system

Abstract

Strain versus field measurements for a ferromagnetic shape memory alloy in the NiMnGa system demonstrate the largest magnetostrictive strains to date of nearly 1.3%. These strains are achieved in the martensitic state through field-induced variant rearrangement. An experimental apparatus is described that provides biaxial magnetic fields and uniaxial compressive prestress with temperature control while recording microstructural changes with optical microscopy. The magnetostrictive response is found to be sensitive to the initial state induced by stress-biasing the martensitic variant structure, and exhibits rate effects related to twin boundary mobility. Experiments performed with constant stress demonstrate work output capacity. Experimental results are interpreted by using a theory based on minimization of a micromagnetic energy functional that includes applied field, stress, and demagnetization energies. It is found that the theory provides a good qualitative description of material behavior, but significantly overpredicts the amount of strain produced. Issues concerning the martensitic magnetic anisotropy and variant nucleation are discussed with regard to this discrepancy.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. of Minnesota, Minneapolis, MN (US)
Sponsoring Org.:
US Department of the Navy, Office of Naval Research (ONR); Advanced Research Projects Agency; National Science Foundation (NSF)
OSTI Identifier:
20000596
Resource Type:
Journal Article
Journal Name:
IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers)
Additional Journal Information:
Journal Volume: 35; Journal Issue: 5Pt3; Other Information: PBD: Sep 1999; Journal ID: ISSN 0018-9464
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SHAPE MEMORY EFFECT; CRYSTAL-PHASE TRANSFORMATIONS; FERROMAGNETISM; MAGNETIC FIELDS; MICROSTRUCTURE; DOMAIN STRUCTURE; NICKEL ALLOYS; MANGANESE ALLOYS; GALLIUM ALLOYS

Citation Formats

Tickle, R., James, R.D., Shield, T., Wuttig, M., and Kokorin, V.V. Ferromagnetic shape memory in the NiMnGa system. United States: N. p., 1999. Web. doi:10.1109/20.799080.
Tickle, R., James, R.D., Shield, T., Wuttig, M., & Kokorin, V.V. Ferromagnetic shape memory in the NiMnGa system. United States. doi:10.1109/20.799080.
Tickle, R., James, R.D., Shield, T., Wuttig, M., and Kokorin, V.V. Wed . "Ferromagnetic shape memory in the NiMnGa system". United States. doi:10.1109/20.799080.
@article{osti_20000596,
title = {Ferromagnetic shape memory in the NiMnGa system},
author = {Tickle, R. and James, R.D. and Shield, T. and Wuttig, M. and Kokorin, V.V.},
abstractNote = {Strain versus field measurements for a ferromagnetic shape memory alloy in the NiMnGa system demonstrate the largest magnetostrictive strains to date of nearly 1.3%. These strains are achieved in the martensitic state through field-induced variant rearrangement. An experimental apparatus is described that provides biaxial magnetic fields and uniaxial compressive prestress with temperature control while recording microstructural changes with optical microscopy. The magnetostrictive response is found to be sensitive to the initial state induced by stress-biasing the martensitic variant structure, and exhibits rate effects related to twin boundary mobility. Experiments performed with constant stress demonstrate work output capacity. Experimental results are interpreted by using a theory based on minimization of a micromagnetic energy functional that includes applied field, stress, and demagnetization energies. It is found that the theory provides a good qualitative description of material behavior, but significantly overpredicts the amount of strain produced. Issues concerning the martensitic magnetic anisotropy and variant nucleation are discussed with regard to this discrepancy.},
doi = {10.1109/20.799080},
journal = {IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers)},
issn = {0018-9464},
number = 5Pt3,
volume = 35,
place = {United States},
year = {1999},
month = {9}
}