New composite functional material with shape memory effect (SME) has recently been proposed and tested for actuation on microscale. The composite nanotweezers have been designed and tested in manipulation of nano-objects. This report presents the new experiments on shape memory alloy’s (SMAs) properties on submicron scale of dimensions and the development of the technology of nanomanipulation on their bases. The minimal thickness of shape memory layer that undergoes SME was experimentally estimated for Ti2NiCu alloy. Impact of the focused ion beam modification of SMA superficial layer on the shape memory properties of micro-sized samples is discussed. Composite actuator of Ni–Mn–Ga magnetic SMA with the size of 20×4×2μm3 was fabricated for the first time and its thermal actuation was experimentally demonstrated (http://www.smwsm.org/microactuators/NiMnGa.html).

This paper deals with the study of magnetoelectric structures which could allow the emergence of a new class of microwave tunable devices. Our interest was focused on composite magnetoelectric structures which associate piezoelectric substrates and magnetostrictive layers in order to get a variation of microwave permeability thanks to an electric field. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers and lead magnesium niobate-lead titanate (PMN-PT) single crystals were used to introduce strains in ferromagnetic layers. Thus, FeCoB/P(VDF-TrFE) and FeCoB/PMN-PT multilayers were investigated through static and dynamic measurements. We demonstrated a strong magnetoelectric effect in a FeCoB/PMN-PT bilayer. Indeed, the FeCoB film permeability decreases from 800 to 1 under 125 V in the 0.5-1.3 GHz frequency band.

This work gives experimental evidence of a promising method of thermal-to-electric energy conversion by coupling shape memory effect (SME) and direct piezoelectric effect (DPE) for harvesting quasi-static ambient temperature variations. Two original prototypes of thermal energy harvesters have been fabricated and tested experimentally. The first is a hybrid laminated composite consisting of TiNiCu shape memory alloy (SMA) and macro fiber composite piezoelectric. This composite comprises 0.1 cm(3) of active materials and harvests 75 mu J of energy for each temperature variation of 60 degrees C. The second prototype is a SME/DPE 'machine' which uses the thermally induced linear strains of the SMA to bend a bulk PZT ceramic plate through a specially designed mechanical structure. The SME/DPE 'machine' with 0.2 cm(3) of active material harvests 90 mu J over a temperature increase of 35 degrees C (60 mu J when cooling). In contrast to pyroelectric materials, such harvesters are also compatible with both small and slow temperature variations.

We report on the dependence of the converse magnetoelectric effect (CME) on the composition of Co60Fe20B20, Co43Fe43B14 and Co28Fe52B20 soft magnetic layers when coupled with PZT-micro-fiber-composites (MFC). In all cases we show strong CME responses, with squareness reduction of 60-80% when increasing the E-field from -1 to +1.4 MV/m. The highest CME response is found for Co43Fe43B14 which shows the largest ratio between the magnetostriction coefficient lambda(s) and the saturation magnetization M-s among the three compositions. According to the quasi-static magnetoelectric converse theory, the linear coupling factor alpha up to 1.65 mu s/m and voltage coefficient M-EH up to 250 V.cm(-1).Oe(-1) are calculated, which is 2-3 orders of magnitude higher than usually reported. (C) 2012 American Institute of Physics. [doi:10.1063/1.3679443]

An enhanced scheme for a functional bilayered composite material with shape memory effect has been successfully applied on the microscale to fabricate a thermally controlled microactuator. Fabrication of cantilever-type microactuators from melt spun ribbon of TiNiCu shape memory alloy included electro-chemical polishing followed by focused ion beam milling and ion-assisted chemical vapor deposition of Pt elastic layer. The smallest working microactuator had a volume of 0.9 µm3. The structure and thermal stability of the Pt layer have been investigated. The fabricated actuator has been proposed for use as micromechanical nanotweezers for manipulation of submicron- and nano-sized objects. Manipulation of a carbon nanotube bunch has been demonstrated.

Ce travail de these porte sur l'etude de composites magnetoelectriques laminaires dans le but de realiser des dispositifs innovants integres sur silicium tel que l'inductance RF variable. Grâce au couplage mecanique entre des couches adjacentes magnetostrictive ultra douce et piezoelectrique, il est possible d'obtenir un couplage magnetoelectrique indirect qui est superieur de plusieurs ordres de grandeur a celui des materiaux multiferroiques naturels. Dans un premier temps, nous avons utilise l'approche phenomenologique basee sur les energies pour decrire le panorama des effets attendus dans des composites magnetoelectriques laminaires (multicouches). Ensuite, des composites magnetoelectriques macroscopiques a base de substrats piezoelectriques de type MFC et de couches minces de FeCoB ont ete realises. L'etude du couplage magnetoelectrique en fonction de la composition de FeCoB a permis de determiner les proprietes cles des materiaux, notamment le rapport λs/Ms, qui sont essentielles pour obtenir un effet magnetoelectrique eleve. Un coefficient magnetoelectrique record de 250 V∙cm‐1Oe‐1 a ete obtenu. Par ailleurs, un microscope a effet Kerr a ete specialement developpe pour pouvoir observer de maniere quasi-instantanee la modification de la structure en domaines sous l'effet de la tension electrique dans ces composites. Pour la premiere fois, l'observation directe de la rotation de l'axe facile d'aimantation sous commande electrique a ete realisee. La deuxieme partie de ce manuscrit est consacree a la conception, simulation, fabrication et caracterisation d'un dispositif MEMS hybride d'inductance variable integree. Ce dispositif exploite l'effet magnetoelectrique indirect entre un element moteur en PZT (sol gel) et un element inductif a base de FeCoB. Etant donne le caractere multiphysique hors norme de ce dispositif, un ensemble de tests electriques, mecaniques, optiques et magnetiques a ete deploye tout au long de la fabrication. Les resultats concluent a une preuve de concept partiellement fonctionnelle en raison principalement d'une mauvaise gestion des contraintes internes liees a la fabrication. Les pistes d'amelioration aux niveaux du design, des materiaux et des procedes sont identifiees.

In this paper, harvesters coupling magnetostrictive and piezoelectric materials are investigated. The energy conversion of quasi-static magnetic field variations into electricity is detailed. Experimental results are exposed for two macroscopic demonstrators based on the rotation of a permanent magnet. These composite/hybrid devices use both piezoelectric and magnetostrictive (amorphous FeSiB ribbon or bulk Terfenol-D) materials. A quasi-static (or ultra-low frequency) harvester is constructed with exploitable output voltage, even in quasi-static mode. Integrated micro-harvesters using sub-micron multilayers of active materials on Si have been built and are currently being characterized.

A study of the magnetoelectric effect is done in a laminated sandwich composite of magnetically soft high-permeability ribbons of Fe-Co-Si-B (Metglas) alloy and piezoelectric macrofiber c composites (PMFC). It is shown that high values of Metglas magnetic permeability result in high values of magnetostrictive susceptibility thus compensating for moderate magnetostriction constants of Metglas and making it competitive with giant magnetostriction alloys of the Terfenol type. High magnetoelectric voltage coefficients of the studied composites enable to use them in various devices including sensors, transducers, energy harvesters and other magnetoelectric devices.

A push-pull type ferromagnetic (FM)/ferroelectric (FE) composite was realized with depositing soft magnetostrictive amorphous (Fe65Co35)80B20 alloy on top of the microfiber lead zirconate titanate commercial composite. The piezoelectric and magnetic hysteresis loops of the FM/FE composite were measured with different electric field polarization. We report a remarkable large converse magnetoelectric effect at room temperature including reversible tuning of the in-plane uniaxial anisotropy. The experimental results were analyzed based on strain-induced magnetization change theory. For this purpose, the applied stress to FM resulting from the piezoelectric strain of FE and the saturation magnetostriction of FM were evaluated. The results indicate a high magnetostriction constant value of 110 ppm and moderate useful applied stress of ± 50 MPa. We conclude that the combination of soft magnetostrictive FM with push-pull type piezoelectric FE is suitable for ultralow power electric field writable or tunable electronic devices.

The increasing demand in alternative energy sources for low-power electronics gives rise to substantial research activity in the field of energy harvesting devices in recent years. Among the different energy sources, thermal sources can be used to produce electrical energy by means of thermoelectric materials, which exploit Seebeck effect [1], or pyroelectric materials [2]. However, thermoelectric devices require large spatial temperature gradients in order to be efficient. In much the same way, pyroelectric materials are inefficient with slow variations of ambient temperature. Nevertheless there is a possibility to convert indirectly thermal energy into electrical energy through mechanical transformations [3]. Taking advantage of the large mechanical deformation (up to 10% [4]) of shape memory alloys (SMA) in the vicinity of their thermally induced phase transition one can convert this mechanical energy into electrical energy with relatively good efficiency by coupling SMA with piezoelectric materials.

Electric field controlled rotation of the magnetization direction of a ferromagnet is investigated in the composite of antiferromagnetic (AF)/ferromagnetic (F)/piezoelectric (PE) layers. Usually, simple 90° magnetization switching is reported with uniaxial F/PE composites. In contrast, when considering unidirectional anisotropy in exchange-biased AF/F systems, a controllable rotation of the magnetization direction in F can be achieved. Here, we show a composite which differs by using in-plane d33 deformation mode with standard magnetic electrodes. We report the experimental evidence of magnetization continuous rotation in IrMn/CoFeB/PZT composites leading to technological impacts on memories, sensors, and microwave devices.

Предложена новая схема композитного функционального материала на основе сплава с эффектом памяти формы (ЭПФ), обеспечивающая гигантскую обратимую изгибную деформацию, при использовании только “одностороннего” ЭПФ сплава. Проведен эксперимент на моделях актюаторов, изготовленных склеиванием быстрозакаленных лент и гальваническим нанесением никеля на предварительно псевдопластически деформированых быстрозакаленных лентах сплава. Показано, что для момента, развиваемого актюатором и его обратимых деформаций теоретические оценки хорошо согласуются с модельными экспериментами. Рассмотрена перспектива применения новой схемы в области микро- и наномеханики. Изготовлены актюаторы с рекордно малыми габаритными размерами методом фокусированного ионного пучка.

We propose a simple yet effective method which allows one to attain large reversible shape changes in shape memory bimetallic composites without training procedure. It is based on the conservation of strongly anisotropic martensite microstructure artificially created in the shape memory layer. This procedure results in appearance of stress field when the shape memory layer is transformed to the austenitic state which brings about two-way shape memory effect. Utilization of this method for preparation of TiNi-based composite with a thickness of 60 µm allowed us to achieve 0.9% reversible bending deformation. It is also suggested that the implementation of this method during preparation of piezoelectric or magnetostrictive composites permits to imprint bias stress and thus to improve their characteristics without use of an external load.

A new scheme of composite functional material based on an alloy exhibiting a shape-memory effect (SME) is proposed. The scheme provides for a giant reversible bending deformation with the use of only “one-way”-SME alloy. An experiment was performed with the use of actuator models manufactured by gluing together the rapidly quenched ribbons and electroplating the pseudoplastically predeformed ribbons of the alloy with nickel. It is shown that the theoretical estimates of the bending moment developed by the actuator and of the reversible deformations of the actuator are in good agreement with the results of the model experiments. The prospects for the use of the new scheme in micro- and nanomechanics are considered. Actuators with record small overall dimensions have been manufactured by the focused ion-beam technique.

New scheme of a functional composite material based on a shape memory alloy has been developed and experimentally tested. The proposed scheme ensures a giant reversible bending deformaion using only one-way shape memory. The scheme has been experimentally implemented on models manufactured by galvanic deposition of nickel onto preliminarily pseudoplastically deformed rapidly quenched Ti50Ni25Cu25 alloy ribbons. The proposed scheme is especially promising for applications in micro- and nanomechanics. In particular, prototype nanotweezers have been manufactured on this basis with record small dimensions of 12 × 3 × 1 μm and a 500-nm-thick shape-memory layer, which is capable of manipulating objects with sizes from 10 to 1000 nm. Controlled deformation of nanotweezers was achieved by heating them using semiconductor laser radiation in a vacuum chamber of scanning ion-probe microscope.

The kinetics of light-induced spin transition and relaxation in [FexZn1-x(phen)(2)(NCS)(2)) (phen=1,10-phenanthroline) has been investigated from time/temperature dependent x-ray powder diffraction with in situ optical excitation. We show that the phase transformation is driven by a heterogeneous nucleation and growth mechanism with phase separation, in both the thermally induced and light-induced regimes. The high spin to low spin isothermal relaxation curves strongly differ from first-order kinetics, and are interpreted using the Kolmogorov-Johnson-Mehl-Avrami model of phase transformation, from which the activation energy to domain growth is derived. Dilution tends to increase the activation energy, and slows down the whole relaxation process. Non-linear photo-induced kinetics as a function of laser power is evidenced, resulting from a light-induced phase separation process; a laser power threshold effect is pointed out. It is found that dilution speeds up the photo-conversion kinetics and reduces the laser power threshold.