Magnetic mosaics in crystalline tiles: The novel concept of polymagnets (invited)

Issue title: SES 2004

Article type: Research Article

Authors: Sullivan, Matthew R.^a | Pirotta, Steven J.^a | Chernenko, V.A.^b | Wu, G.H.^c | Balasubramanium, G.^a | Hua, Susan Z.^{a; d} | Chopra, Harsh Deep^{a; *}

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

Correspondence: [*] Corresponding author: Professor Harsh Deep Chopra, Tel.: +1 716 645 2593 ext. 2310; Fax: +1 716 645 3875; E-mail: hchopra@eng.buffalo.edu

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.

DOI: 10.3233/JAE-2005-688

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 1-2, pp. 11-23, 2005