International Journal of Applied Electromagnetics and Mechanics - Volume 23, issue 1-2

Authors: Buchelnikov, V.D. | Taskaev, S.V. | Aliev, A.M. | Batdalov, A.B. | Gamzatov, A.M. | Korolyov, A.V. | Kourov, N.I. | Pushin, V.G. | Koledov, V.V. | Khovailo, V.V. | Shavrov, V.G. | Grechishkin, R.M.

Article Type: Research Article

Abstract: The results of direct measurements of the magnetic field induced entropy change in the Ni_{2.19} Mn_{0.81} Ga alloy are presented. It is shown that the largest entropy change in the magnetic field 2.6 T is equal to 11 J/kgK. The experimental data are compared with the theoretical results, obtained with the help of the statistical and molecular field theory.

Keywords: Magnetocaloric effect, ferromagnets, magnetostructural phase transition

DOI: 10.3233/JAE-2006-718

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 65-69, 2006

Authors: Gutierrez, J. | Lázpita, P. | Siruguri, V. | Barandiarán, J.M. | Henry, P. | Chernenko, V.A. | Kanomata, T.

Article Type: Research Article

Abstract: We present results of an extensive neutron diffraction study of the martensitic transformation in Shape Memory Alloys of nominal composition Ni_{55-x} Fe_{19+x} Ga_{26} (x=0, 1, 2) at. % transforming close to room temperature. The x=0 sample shows a martensitic transformation temperature T_{M} ≈ 250 K and Curie temperature T_{C} ≈ 289 K. Neutron measurements for this alloy were performed between 300 K (austenite phase) …and 150 K (martensitic phase). At temperatures T>T_{C} we have found the coexistence of two phases: an L2_{1} phase with space group Fm3m and cell parameter a=5.730Å and a γ-fcc with cubic symmetry and with cell parameter a=3.586Å This second phase was also detected by magnetic measurements, giving rise to a second Curie temperature of about 363 K. Show more

Keywords: Ferromagnetic shape memory alloys, martensitic transformation, neutron diffraction characterization, magnetic properties

DOI: 10.3233/JAE-2006-719

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 71-74, 2006

Authors: L'vov, V.A. | Glavatska, N. | Glavatskiy, I. | Ge, Y. | Heczko, O. | Söderberg, O. | Hannula, S.-P.

Article Type: Research Article

Abstract: The isothermal time-dependent deformation of the ferromagnetic Ni-Mn-Ga martensite in the steady magnetic field has been studied both experimentally and theoretically. The role of long wavelength thermal phonons in the deformation process has been disclosed by means of evaluation of the fluctuating mechanical stress, which these phonons induce inside the experimentally observed elements of martensitic structure. A simple relationship between the magnitude of effective fluctuating stress, temperature-dependent elastic modulus and twin width …has been derived. In this way, a strong interdependence between the twin width and the effect of thermal phonons on the twin structure is predicted. The fluctuation mechanism of reversibility of the magnetically induced deformation has been deduced from the experimental and theoretical results. Show more

Keywords: Ferromagnetic martensite, magnetic aftereffects, structure, thermal phonons

DOI: 10.3233/JAE-2006-721

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 75-79, 2006

Authors: Goryczka, T. | Gigla, M. | Morawiec, H.

Article Type: Research Article

Abstract: Polycrystalline 51.2at%N 27.6at%Mn and 21,1at% Ga bulk samples were quenched after annealing at 700°C, 800°C and 900°C for one hour. The parent phase, in sample quenched from 900°C, reveals the B2 structure whereas in the sample quenched from 700°C – the Heusler's structure L2_{1} . The ordering transformation was confirmed by the results obtained from high temperature DSC measurement. On a heating curve broad thermal peak appeared …in the range between 700°C and 800°C. Increasing of the quenching temperature results in lowering temperatures of the martensitic transformation and simultaneously broadens its thermal range. Independently on the quenching temperature and the ordering of the parent phase the martensite shows the 10M structure type. However, in electron diffraction pattern, taken for the sample quenched from 800°C, additional effects of the diffusion electron scattering have been observed as a result of a short-range ordering caused by the Ni exceeding atoms. Show more

Keywords: NiMnGa alloy, five-layer martensite, thermal treatment

DOI: 10.3233/JAE-2006-726

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 81-88, 2006

Authors: Dubowik, J. | Kudryavtsev, Y.V. | Gościańska, I.

Article Type: Research Article

Abstract: We report results of ferromagnetic resonance measurements on sputtered Ni_{x} Mn_{y} Ga_{z} films of various compositions annealed from 620–973 K. Anomalous magnetic behavior of the Ni-Mn-Ga films annealed at T<800 K results from their columnar microstructure and changes in the magnetic anisotropy due to the martensitic transformation. The films annealed at the highest temperatures have the magnetic behavior typical of normal ferromagnetic films, in which the …effect of the martensitic transformation is strongly reduced due to constraint of a substrate. Show more

Keywords: Magnetic shape memory alloys, thin films, ferromagnetic resonance

DOI: 10.3233/JAE-2006-729

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 89-92, 2006

Authors: Sánchez-Alarcos, V. | Pérez-Landazábal, J.I. | Recarte, V. | Gómez-Polo, C. | Chernenko, V.A.

Article Type: Research Article

Abstract: The internal friction, the elastic modulus and the AC magnetic susceptibility of a near stoichiometric Ni2MnGa polycrystalline sample with low transition temperatures have been measured as a function of temperature by resonant ultrasound spectroscopy (RUS) and superconducting quantum interference device (SQUID) measurements. An internal friction peak and two minima in the elastic modulus have been observed, corresponding to the weakly first order transition from the cubic L2_{1} parent phase to the …intermediate phase (at T_{I} ≅ 213 K) and to the Martensitic Transformation (at T_{M} ≅ 100 K). The real part of the magnetic susceptibility shows a decrease and the imaginary part a peak at T_{I} . Show more

Keywords: Ni_{2}MnGa alloy, Pre-martensitic phenomena, Resonant ultrasound spectroscopy, Magnetic susceptibility

DOI: 10.3233/JAE-2006-731

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 93-98, 2006

Authors: Brugger, D. | Kohl, M. | Krevet, B.

Article Type: Research Article

Abstract: A Ni-Mn-Ga microscanner has been developed as a test platform for an experimentally study of the coupled thermal, magnetic and mechanical performance of ferromagnetic shape memory alloy (FSMA) actuators. The microscanner is designed as a double-beam cantilever of a magnetron sputtered Ni-Mn-Ga thin film. The chemical composition of the cantilever is adjusted to simultaneously induce a ferromagnetic and a martensitic phase transformation upon heating. In the presence of a magnetic field, this system can be actuated …in two opposite directions by making use of either magnetic or shape recovery forces. Experimental stationary deflections of the actuator are analyzed by finite element simulations. The shape recovery and magnetic forces are calculated along the trajectory of the actuator allowing the determination of stationary equilibrium positions. Show more

DOI: 10.3233/JAE-2006-722

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 99-105, 2006

Authors: Brugger, D. | Kohl, M. | Hollenbach, U. | Kapp, A. | Stiller, C.

Article Type: Research Article

Abstract: A microscanner system for optical sensing of angle and distance is presented, which is controlled by a ferromagnetic shape memory (FSMA) microactuator. The main features of the FSMA microactuator are a large scanning angle up to 60 deg and a large bandwidth of frequencies given by a broad off-resonance regime below the thermal cut-off frequency at about 120 Hz and the resonance regime between 160 and 220 Hz. The small size and low mass of the …FSMA microactuator allows the design of a very compact and robust scanner system, which enables new portable and mobile applications. In this paper, the sensing of objects in road traffic is pursued as an application in the automotive field, which requires small moving masses being insensitive to vibrations and shock. The main components of the microscanner system are the FSMA microactuator, a pulsed laser diode, an integrated angle sensor, an avalanche diode and a time-of-flight measurement setup for distance acquisition. The maximum scanning range of the first prototype is about 30 m for cooperative (reflecting) objects. The angular resolution is about 0.5°. Show more

DOI: 10.3233/JAE-2006-714

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 107-112, 2006

Authors: Vitushinsky, Roman | Khelfaoui, Fadila | Schmitz, Sam | Winzek, Bernhard

Article Type: Research Article

Abstract: A new mechanism to switch thin film actuators between two stable states has been developed. Bistable membrane switches can be realized by snap-dome shaped metallic foils which are coated on opposite surfaces with Ti(Ni,Cu) and (Ti,Hf)Ni respectively whereby the narrow hysteresis of Ti(Ni,Cu) is within the broad one of (Ti,Hf)Ni. If both SMAs are martensitic or both are austenitic, they apply similar forces on the intermediate foil and the shape of the membrane remains constant. However, …if one of them is austenitic and the other one martensitic, the austenitic one determines the curvature of the membrane. Switching is possible by two different heat pulses. Therefore, energy is only required to change the state of the membrane. The new mechanism is described and first successful processing steps are presented. The mechanism allows the fabrication of microswitches and tactile displays. Show more

DOI: 10.3233/JAE-2006-720

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 113-118, 2006

Authors: Lee, Yun-Jung | Son, Hyung-min | Gu, Jun-bum | Nam, Tae-hyun

Article Type: Research Article

Abstract: To balance the control complexity and number of controlled positions, a novel multi-step SMA actuator is proposed that has multiple controlled positions and can be actuated by sensor-less and open-loop control. The proposed multi-step SMA actuator is constructed so that several electrical taps are connected to one SMA wire and the sections between the taps are all the same length. The controlled positions then vary stepwise according to the number of actuated sections. To control the …multi-step SMA actuator, a PWM(pulse width modulated) voltage with an appropriate duty ratio is applied to designated sections while considering the resistance value of the sections, as well as the recommended current for the given SMA wire. To verify the effectiveness of the proposed multi-step SMA actuator, experiments were performed using a single nitinol wire actuator with a bias spring mechanism and electronic control system. Show more

DOI: 10.3233/JAE-2006-725

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 119-124, 2006