NiMnGa/Si Shape Memory Bimorph Nanoactuation

Lambrecht, Franziska; Lay, Christian; Aseguinolaza, I. R.; Chernenko, V.A.; Kohl, Manfred

doi:10.1007/s40830-016-0080-1

Cited by 14 publications

(4 citation statements)

References 37 publications

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“…Thin films, epitaxially grown on a substrate, exhibit many more constrains from the substrate that result into difficulties for them to show uniform deformations. Nonetheless, they are promising candidates, especially in cantilever or free-standing form, for their implementation in different industrial applications, such as Micro-Electro-Mechanical Systems (MEMS) and Micro-Magneto-Mechanical Systems (MMMS) [13,28,29].…”

Section: Magnetic Shape Memory Alloys Msmasmentioning

confidence: 99%

Neutron Scattering as a Powerful Tool to Investigate Magnetic Shape Memory Alloys: A Review

Río-López

Lázpita

Salazar

et al. 2021

Metals

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Magnetic shape memory alloys (MSMAs) are an interesting class of smart materials characterized by undergoing macroscopic deformations upon the application of a pertinent stimulus: temperature, stress and/or external magnetic fields. Since the deformation is rapid and contactless, these materials are being extensively investigated for a plethora of applications, such as sensors and actuators for the medical, automotive and space industries, energy harvesting and damping devices, among others. These materials also exhibit a giant magnetocaloric effect, whereby they are very promising for magnetic refrigeration. The applications in which they can be used are extremely dependent on the material properties, which are, in turn, greatly conditioned by the structure, atomic ordering and magnetism of a material. Particularly, exploring the material structure is essential in order to push forward the current application limitations of the MSMAs. Among the wide range of available characterization tools, neutron scattering techniques stand out in acquiring advanced knowledge about the structure and magnetism of these alloys. Throughout this manuscript, a comprehensive review about the characterization of MSMAs using neutron techniques is presented. Several elastic neutron scattering techniques will be explained and exemplified, covering neutron imaging techniques—such as radiography, tomography and texture diffractometry; diffraction techniques—magnetic (polarized neutron) diffraction, powder neutron diffraction and single crystal neutron diffraction, reflectometry and small angle neutron scattering. This will be complemented with a few examples where inelastic neutron scattering has been employed to obtain information about the phonon dispersion in MSMAs.

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Section: Magnetic Shape Memory Alloys Msmasmentioning

confidence: 99%

Neutron Scattering as a Powerful Tool to Investigate Magnetic Shape Memory Alloys: A Review

Río-López

Lázpita

Salazar

et al. 2021

Metals

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“…Thin film technology of the FSMAs has been under intense development and research during last decade (see Ref. and references therein) to explore a potential of these films for actuation and caloric applications on the micro(nano)scale.…”

Section: Anhysteretic Behavior Of Ferromagnetic Sma Films and Nanobeamsmentioning

confidence: 99%

Large Anhysteretic Deformation of Shape Memory Alloys at Postcritical Temperatures and Stresses

Chernenko

L'vov

Kabra

et al. 2017

Physica Status Solidi (b)

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Magnetic and nonmagnetic shape memory alloys (SMAs) exhibit thermoelastic martensitic transformations (MTs) which are hysteretic due to their first-order nature. According to the thermodynamic Landau theory of phase transitions, which assumes ideal thermoelastic equilibrium at each point of the MT interval, the hysteresis is explained by the different limits of stability for austenite and martensite in the phase diagram. No interactions on the phase boundaries are taken into account. In the real alloys, the hysteresis of MT is related not only to the stability intervals of two phases but also to the processes of nucleation and growth of the resultant phase inside the parent phase. In turn, the features of these processes are related to the heights of energy barriers caused by the incompatibility of austenitic and martensitic lattices, crystal defects and some other physical factors. However, the defects, normally, play a minor role in the width of MT hysteresis if compared to the thermodynamic and crystallographic factors. A reduction of hysteresis of MT in SMAs, being crucial for technology, presents a challenging problem for science. A decrease of hysteresis width of MT was observed recently for the single crystals of ferromagnetic SMAs such Ni-Fe(Co)-Ga and Fe-Pd on approaching of their transformation paths to the critical point in stresstemperature phase diagram. Moreover, the superelastic and shape memory properties characterized by the nearly-zero hysteresis width were observed in the postcritical transformational regime. Here we show that both the Landautype theory of ferroelastic phase transitions and neutron diffraction experiments carried out under axial compression describe the essential features of these properties. We also interpret the experimentally observed anhysteretic phenomena in Ni-Mn-Ga thin films and nanobeam actuators in terms of their postcritical state.

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“…Different pioneering works have been dedicated in down-scaling MSM Heuslers using several bottom-up and top-down approaches [16][17][18]. Specifically, starting from thin films of MSM Heuslers, the down-scaling approaches have been limited to nanosphere-lithography [15], photolithography [13,19,20], electron-beam lithography [6,[21][22][23][24][25][26] and focused ion-beam milling techniques [27,28].…”

Section: Introductionmentioning

confidence: 99%

Dewetting Process in Ni-Mn-Ga Shape-Memory Heusler: Effects on Morphology, Stoichiometry and Magnetic Properties

et al. 2022

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In this work, dewetting process has been investigated in shape-memory Heuslers. To this aim, series of high-temperature annealing (1100–1150 K) have been performed at high vacuum (time is varied in the range of 55–165 min) in Ni-Mn-Ga epitaxial thin films grown on MgO(001). The process kinetics have been followed by studying the evolution of morphology and composition. In particular, we report the initiation of the dewetting process by the formation of symmetric holes in the films. The holes propagate and integrate, leaving micrometric and submicron islands of the material, increasing the average roughness of the films by a factor of up to around 30. The dewetting process is accompanied by severe Ga and Mn sublimation, and Ni-Ga segregation, which significantly modify the magnetic properties of the films measured at each stage. The annealed samples show a relatively weak magnetic signal at room temperature with respect to the pristine sample.

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NiMnGa/Si Shape Memory Bimorph Nanoactuation

Cited by 14 publications

References 37 publications

Neutron Scattering as a Powerful Tool to Investigate Magnetic Shape Memory Alloys: A Review

Neutron Scattering as a Powerful Tool to Investigate Magnetic Shape Memory Alloys: A Review

Large Anhysteretic Deformation of Shape Memory Alloys at Postcritical Temperatures and Stresses

Dewetting Process in Ni-Mn-Ga Shape-Memory Heusler: Effects on Morphology, Stoichiometry and Magnetic Properties

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