A Model for Ferromagnetic Shape Memory Thin film Actuators

Stefan Seelecke 1Kwok-Lun Lee 

1. North Carolina State University (NCSU), 3211 Broughton Hall, Raleigh, NC 27695, United States

Abstract

The last decade has witnessed the discovery of materials combining shape memory behavior with ferromagnetic properties (FSMAs). These materials feature the so-called giant magnetostrain effect, which, in contrast to conventional magnetostriction is due motion of martensite twins. This effect has motivated the development of a new class of active materials transducers, which combine intrinsic sensing capabilities with superior actuation speed and improved efficiency when compared to conventional shape memory alloys.

Currently, thin film technology is being developed intensively in order to pave the way for applications in micro- and nanotechnology. As an example, Kohl et al., 2004a, recently proposed a novel actuation mechanism based on NiMnGa thin film technology, which makes use of both the ferromagnetic transition and the martensitic transformation allowing the realization of an almost perfect antagonism in a single component part. Possible applications in nanotechnology arise, e.g., by combination of smart NiMnGa actuators with scanning probe technologies.

The research presented in this paper aims at the development of a model that simulates the material behavior of the above device. It uses a model originally developed for conventional shape memory alloy behavior by Mueller, Achenbach, and Seelecke and couples it with an expression for the nonlinear temperature- and position-dependent effective magnetic force. Even though the model does not account for full coupling between SMA behavior and ferromagnetism yet, it shows the potential to predict the effect of different Curie temperatures on the device performance and will eventually allow optimizing material properties for a specific application.

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium C, by Stefan Seelecke
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-23 17:15
Revised:   2009-06-07 00:44
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