Goodfellow is delighted to announce the addition of an exciting new product to our range - Magnetic Shape Memory Material.
What is magnetic shape memory (MSM) effect or magnetic-field-induced reorientation (MIR)?
"Magnetic-field-induced rearrangement of (ferromagnetic) twinned martensite microstructure accompanied by a large macroscopic deformation." This patented NiMnGa single crystal material has some extremely innovative properties:
The magnetic shape memory effect can be used to design actuators, where the element elongates based on the presence of a magnetic field. The elongation is fully reversible, either by applying a magnetic field at 90° to the original field, or more effectively by use of a spring. The shape change is very rapid, and cycle times of 1 to 2 kHz have been shown. Several hundred million cycles have been achieved while testing fatigue life.
Whilst not achieving the frequency of piezo-based materials or magnetostrictive materials, magnetic shape memory materials give much higher strain outputs (typically 10 to 100 times more). They also provide higher energy density, typically up to 100kJm-3 compared to 14 to 30kJm-3 for magnetostrictive materials and 0.8 to 2kJm-3 for piezo-based materials.
The additional thermal shape memory property, whereby the material elongates even further above 70°C can be used as a safety cut-out. The actuator runs until the safe working temperature is reached whereupon it extends further, cutting the magnetic field generation. This additional elongation is fully reversible, and below 70°C the actuator functions normally again.
Compressing or elongating this material causes it to alter any magnetic field in which it is placed (variable magnetic permeability under varying stress), which can be used to “harvest” vibration energy. Possible uses include battery charging in environments where it is difficult to gain access to the batteries for replacement.
The same properties used to create energy harvesters can be used to damp mechanical vibration.
Using the material’s properties, it is possible to construct speed sensors as well as distance, strain and magnetic field detectors.
In order to minimize the magnetic energy required to elongate the material, a thin, wide cross-section is preferred, and as the elongation is a multiple of the length, a comparatively long strip is also preferred. Therefore, Goodfellow is offering this material in the following dimensions:
1 mm thickness x 2.5 mm width x 20mm length
1 mm thickness x 5 mm width x 20mm length
2 mm thickness x 5 mm width x 20mm length
These are our standard dimensions, but other dimensions are of course available on request. Currently, the maximum single crystal size is 18mm diameter x 30mm length. Smaller pieces are cut from within the above dimensions using special techniques to preserve the performance of the material. Development work is underway to produce larger crystals, and as these become available we will keep you informed via our website.