International Journal of Applied Electromagnetics and Mechanics - Volume 12, issue 1-2

Article Type: Editorial

Abstract: Preface to the SMART-2000 special issue.

DOI: 10.3233/JAE-2000-187

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 1-2, 2000

Authors: Chernenko, V.A. | L'vov, V.A. | Pasquale, M. | Besseghini, S. | Sasso, C. | Polenur, D.A.

Article Type: Research Article

Abstract: The magnetostriction measurements of almost stoichiometric single crystalline Ni_2 MnGa compound with T_m<T_C (T_m and T_C are the martensitic and ferromagnetic transformation temperatures respectively) at constant temperatures have been performed in a temperature range of 100--400 K. The measurements resulted in a temperature evolution of magnetostrain, \varepsilon , with two extremums caused by soft mode condensation and martensitic transformation. Magnetic field induced …strain of 0.4% In turn, the dilatometric mode of measurements along [100] under magnetic field (either constant or cyclic) led to 1.5% strain in martensite. Using a phenomenological approach both the anisotropic and volume magnetoelastic constants have been evaluated in cubic phase to be equal to - 1.2 MPa and - 0.4 GPa respectively. The experimentally observed smearing of Curie temperature in single crystalline Ni_{51.2} Mn_{31.1} Ga_{17.7} alloy with T_m>T_C is quantitatively explained by the spatially inhomogeneous mass density of martensitic phase and volume magnetostriction. Show more

DOI: 10.3233/JAE-2000-201

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 3-8, 2000

Authors: Hosoda, Hideki | Sugimoto, Tsuyoshi | Ohkubo, Kenji | Miura, Seiji | Mohri, Tetsuo | Miyazaki, Shuichi

Article Type: Research Article

Abstract: Martensitic and magnetic transformation temperatures were investigated for Ni_2 MnGa alloys as a function of the degree of long-range order (LRO) associated with L2_1 structure. The degree of order was changed by changing the heat treatment temperature. Besides, thermal properties such as thermal expansion (CTE), specific heat (C_P ) and thermal conductivity (\lambda ) were measured up to 1273 K. It was found that with increasing the heat …treatment temperature, the degree of second neighbor ordering lowered, but that the degree of first neighbor ordering did not show good correlations with the heat treatment temperatures. Martensitic transformation temperature (M_s ) and Curie temperature (T_C ) vary with the square of the degree of LRO.C_P and \lambda at room temperature are 29.5 Jmol^{-1} K^{-1} and 23.2 Wm^{-1} K^{-1} . CTE is ranged between 15 \times 10^{-6} K^{-1} and 34 \times 10^{-6} K^{-1} . Temperature dependence of these thermal properties is described. Show more

Keywords: Ni_2MnGa, long range order, L2_1 structure, Curie temperature, martensitic transformation temperature, thermal expansion, specific heat, heat treatment

DOI: 10.3233/JAE-2000-189

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 9-17, 2000

Authors: Buchelnikov, V. | Zayak, A. | Vasil'ev, A. | Takagi, T.

Article Type: Research Article

Abstract: In the framework of Landau theory the phase diagram of structural and magnetic phase transitions of cubic ferromagnetic Ni-Mn-Ga alloys is constructed by taking into account the strain, the crystal lattice modulation and the magnetic order parameters.

DOI: 10.3233/JAE-2000-188

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 19-23, 2000

Authors: Inoue, Kazuko | Enami, Kazuyuki | Igawa, Masafumi | Yamaguchi, Yasuo | Ohoyama, Kenji | Morii, Yukio | Matsuoka, Yuki | Inoue, Kanryu

Article Type: Research Article

Abstract: We have made the Heusler-type Ni_2 MnGa-based alloys, Ni_{2.18} Mn_{0.82} Ga, Ni_{2.19} Mn_{0.81} Ga and Ni_2 Mn_{0.92} Ga_{1.08} , which have the martensitic transformation temperature coincident with the Curie temperature. The powder neutron diffraction measurements of these alloys were performed. The Rietveld analysis of the diffraction patterns showed that at least two crystal structures coexist in each martensitic phase. For …Ni_{2.18} Mn_{0.82} Ga and Ni_{2.19} Mn_{0.81} Ga, the main structure is a monoclinic one with a six-layers shuffling and a small amount of orthorhombic structure distorted from the cubic Heusler one is included. For Ni_2 Mn_{0.92} Ga_{1.08} , the main structure is tetragonal whereas a small amount of other structures seem to be included. The neutron diffraction of Ni_{2.19} Mn_{0.81} Ga under magnetic field up to 5 T at the coincident transformation temperature of 350 K shows that the magnetic field causes the phase transformation from cubic phase to martensitic one. The result suggests the possibility of controlling the shape memory effect originating from the thermoelastic martensitic transformation, by applying the external magnetic field instead of changing the temperature. Show more

DOI: 10.3233/JAE-2000-197

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 25-33, 2000

Authors: Vasil'ev, A.N. | Estrin, E.I. | Khovailo, V.V. | Bozhko, A.D. | Ischuk, R.A. | Matsumoto, M. | Takagi, T. | Tani, J.

Article Type: Research Article

Abstract: A study of polycrystalline and single crystalline Ni_{2+X} Mn_{1-X} Ga alloys by means of dilatometric and strain gage techniques shows that large strain can be induced in the temperature range of the martensitic transformation by application of an external magnetic field. The biggest strain induced by magnetic field was observed in the samples of chemical compositions where the structural and magnetic transitions couple, i.e. occur at the same temperature.

DOI: 10.3233/JAE-2000-198

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 35-40, 2000

Authors: Ishida, Shoji | Furugen, Munemasa | Asano, Setsuro

Article Type: Research Article

Abstract: The electronic structures of Ni_{2.17} Mn_{0.83} Ga predict that the tetragonal, the orthorhombic and the monoclinic structure can be a martensitic phase and the monoclinic structure is the most stable. The stabilization of the monoclinic structure mainly comes from the difference of the kinetic energy. Then, the Ni excess plays an important role in the stabilization of the crystal structure. The Ni excess atoms make the tetragonal and orthorhombic structures …unstable and the monoclinic structure stable. It is also found that the Ni excess atoms prefer the Mn sites and the magnetic moments in the monoclinic structure are smaller than those in the other structures. Show more

DOI: 10.3233/JAE-2000-190

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 41-48, 2000

Authors: Ohtsuka, Makoto | Itagaki, Kimio

Article Type: Research Article

Abstract: The effect of heat treatment on the properties of Ni-Mn-Ga films such as chemical composition, crystal structure, microstructure and transformation temperature were investigated with respect to various sputtering conditions. Ni-Mn-Ga films were deposited on a poly-vinyl alcohol substrate with a radio-frequency magnetron sputtering apparatus using Ni_{50} Mn_{25} Ga_{25} and Ni_{52} Mn_{24} Ga_{24} targets. After separating from the substrates, the films …were annealed at temperatures between 873 and 1273 K for 3.6 ks. The chemical composition of the films depended on the sputtering power, but there was no dependence on the heat treatment temperature. Each deposited film had a columnar grain structure. After the heat treatment, the width of the columnar grains increased and then became indistinct with increasing heat treatment temperature. The martensitic transformation temperature increased with increasing nickel content of the films, while the Curie temperature decreased. The film heat-treated at 1073 K showed a two-way shape memory effect through the martensitic transformation and its reversion. Show more

Keywords: nickel-manganese-gallium, microstructure, crystal structure, martensitic transformation, shape memory effect

DOI: 10.3233/JAE-2000-194

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 49-59, 2000

Authors: Wang, Z. | Iijima, T. | He, G. | Takahashi, T. | Furuya, Y.

Article Type: Research Article

Abstract: Fe-30.0 mol%P The thin films were solution-treated at 1173 K for 60 s in vacuum and subsequently cooled by argon gas flow. The as-deposited thin films possess ultra-fine grains resulting in a long-range disorder structure. After the heat treatment, (\gamma Fe, Pd) phase with an fcc structure is re-crystallized and the crystallized thin films show the texture orientation with (111) and (100) planes parallel to the surfaces of the thin films. Magnetic properties of the …thin films are also affected by the crystal structure and grain size. The rectangularity of the hysteresis loop has been improved in the solution-treated thin films. Show more

DOI: 10.3233/JAE-2000-196

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 61-66, 2000

Authors: Yabe, Hiromasa | Oguri, Kazuya | Uchida, Haru-Hisa | Matsumura, Yoshihito | Uchida, Hirohisa | Nishi, Yoshitake

Article Type: Research Article

Abstract: The magnetostriction induced shape memory effect (MSME) was investigated in the Fe-Pd thin films prepared by magnetron sputtering. The reversible relationship was obtained between shape change and applied magnetic field from earth magnetic field to 0.2 kOe. The high magnetostrictive susceptibility were detected at low magnetic field below 0.2 kOe at room temperature. These were higher than that of Tb_{0.3} Dy_{0.7} Fe_2 thin film developed.

Keywords: Fe-Pd alloy, micrograph, crystal structure, magnetostrictive susceptibility

DOI: 10.3233/JAE-2000-192

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 12, no. 1-2, pp. 67-70, 2000