Leaves have turned golden and yellow, the weather is getting cold by the day and I have embraced on a new project. Working away at my new desk doing literature search and shopping for chemical ingredients.
In the begging there is always chaos and the unknown looms blurry in the far distance but as I read on the overall entropy decreases.
The subject of my new scientific encounter are shape memory alloys SMA and in particular ferromagnetic shape memory alloys called FSMAs for short.
Shape memory alloys are a special group of metallic materials, which have the unique ability to restore some predetermined shape or size under the influence of stress, temperature or magnetic field (FSMA). This effect is caused by structural changes occurring over a range of different, external conditions.
Basically what happens here is the following: when cooled below a transformation temperature the high temperature phase called austenite, generally it is has a cubic crystal structure, turns into a low temperature martensitic phase, usually tetragonal. In this phase the material is characterized by a low yield strength and can be deformed to any shape with a relatively low force. This shape is retained as long as the material is kept below the transition temperature. (1) When heated above this temperature it reverts back to its original shape. Thanks to this property the shape memory materials find a plethora of applications including actuator and sensor systems.
A special family amongst these materials are the already above mentioned ferromagnetic materials FSMAs exhibiting shape memory effect when exposed to a magnetic field. This effect was first observed by Ullakko (2) who reported a field-induced strain in Ni2MnGa single crystal in the martensite state. This magnetic field implicated strain arises from the twin boundary rearrangement producing the macroscopic shape change. Since this discovery by Ullakko over a decade ago ferromagnetic shape memory materials have been extensively studied however much is still to be done. In the near future I am hoping to be a new contributor to this fascinating subject.

1. P. Gupta, P.S. Robi, P.P. Singha, A. Srinivasan, Journal of Materials Processing Technology 153–154 (2004) 965–970.
2. M.A. Marioni et all., Journal of Magnetism and Magnetic Materials 290–291 (2005) 35–41.