Affiliations: [a] Thin Films and Nanosynthesis Laboratory, Materials
Program, Mechanical and Aerospace Engineering Department, SUNY-Buffalo,
Buffalo, NY 14260, USA | [b] Institute of Magnetism, Vernadsky Street 36-b, Kiev
03142, Ukraine | [c] State Key Laboratory for Magnetism, Institute of
Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of
China | [d] Department of Physiology and Biophysics, SUNY-Buffalo,
Buffalo, NY 14260, USA
Abstract: This article presents our recent results on magnetic shape memory
alloys (SMAs) and reviews some of our relevant past work. By treating the
martensite structure as an assembly of microscopic crystalline tiles (twins),
the observed micromagnetic structure or 'magnetic mosaic' in these alloys can
be explained in terms of a spatially varying axis of the magnetocrystalline
anisotropy and magnetostatic interactions across the tiles. A systematic
investigation of ferroelastic structural domains of increasing structural
complexity leads to a novel concept of 'polymagnets'. Similar to the idea of
hierarchical ferroelastic polydomains, polymagnets are hierarchical
micromagnetic structures, and parallels the complexity of the underlying
ferroelastic polydomains. Preliminary results on the dynamics of the
transformation pathways reveal a strong correlation between the underlying
microstructure and achievable strain. In addition, reversible shape memory
effect has been observed in sputter-deposited Ni-Mn-Ga thin films, and Co-Ni
films with controlled composition have been successfully made by
electrodeposition.
