Transducers utilizing the Villari effect (inverse-magnetostrictive effect) consist of a coil wound on a core of magnetostrictive material. In this paper, a linear magnetomechanical coupling model is developed to analytically calculate the potential electrical power such transducers can generate when subjected to applied harmonic mechanical vibration. Two vibration modes, force driven and displacement driven, are distinguished. The eddy current effect in the magnetostrictive core material and the leakage inductance of the coil are taken into account. Comparisons of output electrical power are presented for Terfenol-D and Galfenol magnetostrictive cores.

Magnetostrictive multilayer films which combine exchange coupled giant magnetostrictive materials (amorphous Tb0.4Fe0.6) and soft magnetic materials with large polarizations and considerable magnetostriction (crystalline Fe0.5Co0.5) were prepared by magnetron sputtering. The microstructure and the magnetic properties of these multilayers were investigated as a function of the annealing temperatures and the corresponding film stresses. Giant magnetoelastic coupling coefficients (or magnetostrictions) are achieved at low fields, due to the magnetic polarization enhancement in such multilayers, the optimized stress state, and a suitable microstructure. For these optimized Tb0.4Fe0.6(7 nm)/Fe0.5Co0.5(9 nm) multilayers a saturation magnetoelastic coupling coefficient of 27.5 MPa at 20 mT and a coercive field of 2 mT has been achieved.

Magnetic and microstructural investigations of some polycrystalline rare-earth—transition-metal (RE-TM) alloy thin films are reported. Emphasis was placed on pseudobinary alloys in the (TbxDy1−x)Fe2 and (TbxDy1−x)3Fe4 systems. The films were prepared by sputter deposition onto both room-temperature and high-temperature substrates. Films prepared on room-temperature substrates were amorphous and were crystallized by postdeposition annealing. Transmission electron microscopy and x-ray diffraction showed and indicated a complex microstructure consisting of small grains of free iron, REFe compounds, and some RE oxide phases. Magnetization, coercivity, and magnetostriction measurements showed the films to be essentially magnetized in plane with a trend across the composition range which reflected the different influences of Tb and Dy and also the compensation condition. Magnetostriction values greater than 0.75×10−3 were found near the Terfenol composition Tb0.27Dy0.73Fe2 and for x≳0.3.

The effect of furnace annealing on the magnetic and magnetoelastic properties of amorphous wire of composition Fe77.5Si7.5B15 has been investigated. The field dependence of Young’s modulus and magnetization combined with x-ray analysis and scanning electron microscopy have been used to monitor the effects of annealing. The results indicate that progressive annealing leads first to relief of the radial casting stress with a corresponding reduction in angle between the average easy direction and the wire axis. Further annealing leads to surface crystallization for which it is suggested that the moments take up a circumferential orientation. Annealing still further leads to crystallization of the bulk material which greatly increases the anisotropy and greatly reduces the ΔE effect.

The ternary alloy Tb0.3Dy0.7Fe2 (Terfenol-D) is of significant technological interest as it possesses the largest known magnetostriction to anisotropy ratio near room temperature. Results of microstructural and magnetic domain observations by Lorentz microscopy and reflection x-ray topography are presented from both stoichiometric twinned single crystals prepared by a free-standing zoning technique, and pseudo single crystals prepared by the Czochralski method. Direct evidence of wall interactions with dislocations, twin boundaries and precipitates are presented which demonstrate the complex interaction between the magnetic and strain energies within this material.