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31-420: MSMA may refer to: Magnetic shape-memory alloy , a type of shape memory material which responds to magnetic fields Monosodium methyl arsenate Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title MSMA . If an internal link led you here, you may wish to change the link to point directly to

62-428: A different orientation of the elementary cells (the regions are shown by the figure in green and blue colors). These regions are called twin-variants. The application of a magnetic field or of an external stress shifts the boundaries of the variants, called twin boundaries , and thus favors one variant or the other. When the element is completely contracted or completely elongated, it is formed by only one variant and it

93-418: A ferromagnet is superparamagnetic . The observed magnetic anisotropy in an object can happen for several different reasons. Rather than having a single cause, the overall magnetic anisotropy of a given object is often explained by a combination of these different factors: The magnetic anisotropy of a benzene ring (A), alkene (B), carbonyl (C), alkyne (D), and a more complex molecule (E) are shown in

124-529: A lower internal friction, a higher transformation temperature and a higher Curie temperature, which would allow the use of MSM alloys in several applications. In fact, the actual temperature range of standard alloys is up to 50 °C. Recently, an 80 °C alloy has been presented. Due to the twin boundary motion mechanism required for the magnetic shape memory effect to occur, the highest performing MSMAs in terms of maximum induced strain have been single crystals. Additive manufacturing has been demonstrated as

155-485: A technique to produce porous polycrystalline MSMAs. As opposed to fully dense polycrystalline MSMAs, porous structures allow more freedom of motion, which reduces the internal stress required to activate martensitic twin boundary motion. Additionally, post-process heat treatments such as sintering and annealing have been found to significantly increase the hardness and reduce the elastic moduli of Ni-Mn-Ga alloys. MSM actuator elements can be used where fast and precise motion

186-492: Is a function of strain. The most common MSM actuator design consists of an MSM element controlled by permanent magnets producing a rotating magnetic field and a spring restoring a mechanical force during the shape memory cycling. Limitations on the magnetic shape memory effect due to crystal defects determine the efficiency of MSMAs in applications. Since the MSM effect is also temperature dependent, these alloys can be tailored to shift

217-437: Is obtained by the geometric rotation of the elementary cells composing the alloy, and not by rotation of the magnetization vectors within the cells (like in magnetostriction ). A similar phenomenon occurs when the alloy is subjected to an external force. Macroscopically, the force acts like the magnetic field, favoring the rotation of the elementary cells and achieving elongation or contraction depending on its application within

248-550: Is required. They are of interest due to the faster actuation using magnetic field as compared to the heating/cooling cycles required for conventional shape memory alloys, which also promises higher fatigue lifetime. Possible application fields are robotics, manufacturing, medical surgery, valves, dampers, sorting. MSMAs have been of particular interest in the application of actuators (i.e. microfluidic pumps for lab-on-a-chip devices) since they are capable of large force and stroke outputs in relatively small spatial regions. Also, due to

279-404: Is said to be in a single variant state . The magnetization of the MSM element along a fixed direction differs if the element is in the contraction or in the elongation single variant state. The magnetic anisotropy is the difference between the energy required to magnetize the element in contraction single variant state and in elongation single variant state. The value of the anisotropy is related to

310-443: Is the saturation magnetization and α , β , γ {\displaystyle \alpha ,\beta ,\gamma } are direction cosines (components of a unit vector ) so α 2 + β 2 + γ 2 = 1 {\displaystyle \alpha ^{2}+\beta ^{2}+\gamma ^{2}=1} . The energy associated with magnetic anisotropy can depend on

341-427: The MSM technology very attractive for the design of innovative actuators to be used in pneumatics, robotics, medical devices and mechatronics. MSM alloys change their magnetic properties depending on the deformation. This companion effect, which co-exist with the actuation, can be useful for the design of displacement, speed or force sensors and mechanical energy harvesters . The magnetic shape memory effect occurs in

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372-434: The anisotropy constant, and θ {\displaystyle \theta } the angle between the easy axis and the particle's magnetization. When shape anisotropy is explicitly considered, the symbol N {\displaystyle {\mathcal {N}}} is often used to indicate the anisotropy constant, instead of K {\displaystyle K} . In the widely used Stoner–Wohlfarth model ,

403-427: The anisotropy is uniaxial. A magnetic particle with triaxial anisotropy still has a single easy axis, but it also has a hard axis (direction of maximum energy) and an intermediate axis (direction associated with a saddle point in the energy). The coordinates can be chosen so the energy has the form If K a > K b > 0 , {\displaystyle K_{a}>K_{b}>0,}

434-420: The cone of the benzene ring thus the magnetic anisotropy is not present. While the cis form holds proton {H} in the vicinity of the cone, shields it and decreases its chemical shift. This phenomenon enables a new set of nuclear Overhauser effect (NOE) interactions (shown in red) that come to existence in addition to the previously existing ones (shown in blue). Suppose that a ferromagnet is single-domain in

465-486: The crystal structure and twin boundaries. Additionally, inducing a fully strained (elongated or contracted) MSMA has been found to reduce fatigue life, so this must be taken into consideration when designing functional MSMA systems. In general, reducing defects such as surface roughness that cause stress concentration can increase the fatigue life and fracture resistance of MSMAs. Standard alloys are Nickel - Manganese - Gallium (Ni-Mn-Ga) alloys, which are investigated since

496-403: The direction cosines in various ways, the most common of which are discussed below. A magnetic particle with uniaxial anisotropy has one easy axis. If the easy axis is in the z {\displaystyle z} direction, the anisotropy energy can be expressed as one of the forms: where V {\displaystyle V} is the volume, K {\displaystyle K}

527-419: The easy axis is an energetically favorable direction of spontaneous magnetization . Because the two opposite directions along an easy axis are usually equivalently easy to magnetize along, the actual direction of magnetization can just as easily settle into either direction, which is an example of spontaneous symmetry breaking . Magnetic anisotropy is a prerequisite for hysteresis in ferromagnets : without it,

558-449: The easy axis is the z {\displaystyle z} direction, the intermediate axis is the y {\displaystyle y} direction and the hard axis is the x {\displaystyle x} direction. A magnetic particle with cubic anisotropy has three or four easy axes, depending on the anisotropy parameters. The energy has the form If K > 0 , {\displaystyle K>0,}

589-412: The field is applied. This is known as magnetic isotropy . In contrast, magnetically anisotropic materials will be easier or harder to magnetize depending on which way the object is rotated. For most magnetically anisotropic materials, there are two easiest directions to magnetize the material, which are a 180° rotation apart. The line parallel to these directions is called the easy axis . In other words,

620-426: The figure. Each of these unsaturated functional groups (A-D) create a tiny magnetic field and hence some local anisotropic regions (shown as cones) in which the shielding effects and the chemical shifts are unusual. The bisazo compound (E) shows that the designated proton {H} can appear at different chemical shifts depending on the photoisomerization state of the azo groups. The trans isomer holds proton {H} far from

651-480: The first relevant MSM effect has been published in 1996. Other alloys under investigation are Iron - Palladium (Fe-Pd) alloys, Nickel-Iron-Gallium (Ni-Fe-Ga) alloys, and several derivates of the basic Ni-Mn-Ga alloy which further contain Iron (Fe), Cobalt (Co) or Copper (Cu). The main motivation behind the continuous development and testing of new alloys is to achieve improved thermo-magneto-mechanical properties, such as

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682-420: The high fatigue life and their ability to produce electromotive forces from a magnetic flux, MSMAs are of interest in energy harvesting applications. The twinning stress, or internal frictional stress, of an MSMA determines the efficiency of actuation, so the operation design of MSM actuators is based on the mechanical and magnetic properties of a given alloy; for example, the magnetic permeability of an MSMA

713-574: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=MSMA&oldid=933005611 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Magnetic shape-memory alloy MSM alloys are ferromagnetic materials that can produce motion and forces under moderate magnetic fields. Typically, MSMAs are alloys of Nickel, Manganese and Gallium (Ni-Mn-Ga). A magnetically induced deformation of about 0.2%

744-412: The large strain of MSM alloys is the so-called magnetically induced reorientation (MIR), and is sketched in the figure. Like other ferromagnetic materials, MSM alloys exhibit a macroscopic magnetization when subjected to an external magnetic field, emerging from the alignment of elementary magnetizations along the field direction. However, differently from standard ferromagnetic materials, the alignment

775-625: The low temperature martensite phase of the alloy, where the elementary cells composing the alloy have tetragonal geometry. If the temperature is increased beyond the martensite– austenite transformation temperature, the alloy goes to the austenite phase where the elementary cells have cubic geometry. With such geometry the magnetic shape memory effect is lost. The transition from martensite to austenite produces force and deformation. Therefore, MSM alloys can be also activated thermally, like thermal shape memory alloys (see, for instance, Nickel-Titanium ( Ni-Ti ) alloys). The mechanism responsible for

806-432: The maximum work-output of the MSM alloy, and thus to the available strain and force that can be used for applications. The main properties of the MSM effect for commercially available elements are summarized in (where other aspects of the technology and of the related applications are described): The fatigue life of MSMAs is of particular interest for actuation applications due to the high frequency cycling, so improving

837-402: The microstructure of these alloys has been of particular interest. Researchers have improved the fatigue life up to 2x10 cycles with a maximum stress of 2MPa, providing promising data to support real application of MSMAs in devices. Although high fatigue life has been demonstrated, this property has been found to be controlled by the internal twinning stress in the material, which is dependent on

868-410: The reference coordinate system. The elongation and contraction processes are shown in the figure where, for example, the elongation is achieved magnetically and the contraction mechanically. The rotation of the cells is a consequence of the large magnetic anisotropy of MSM alloys, and the high mobility of the internal regions. Simply speaking, an MSM element is composed by internal regions, each having

899-592: The strictest sense: the magnetization is uniform and rotates in unison. If the magnetic moment is μ {\displaystyle {\boldsymbol {\mu }}} and the volume of the particle is V {\displaystyle V} , the magnetization is M = μ / V = M s ( α , β , γ ) {\displaystyle \mathbf {M} ={\boldsymbol {\mu }}/V=M_{s}\left(\alpha ,\beta ,\gamma \right)} , where M s {\displaystyle M_{s}}

930-437: The transition temperature by controlling microstructure and composition. Magnetic anisotropy In condensed matter physics , magnetic anisotropy describes how an object's magnetic properties can be different depending on direction . In the simplest case, there is no preferential direction for an object's magnetic moment . It will respond to an applied magnetic field in the same way, regardless of which direction

961-480: Was presented in 1996 by Dr. Kari Ullakko and co-workers at MIT. Since then, improvements on the production process and on the subsequent treatment of the alloys have led to deformations of up to 6% for commercially available single crystalline Ni-Mn-Ga MSM elements, as well as up to 10-12 % and 20% for new alloys in R&;D stage. The large magnetically induced strain, as well as the short response times make

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