Terfenol-based materials with reduced eddy-current loss for high-frequency applications

Abstract

Eddy-current loss is the principal limitation to the use of Terfenol for high-frequency applications. Silicon-doped Terfenol materials, developed with the aim of reducing eddy-current loss to improve high-frequency performance, are described and compared with a composite, polymer-bonded Terfenol. Alloys with 1, 2 and 4 Wt% Si in Tb_0.27Dy_0.73Fe₂ were prepared. The resistivity is shown to increase significantly, with 2% Si giving a threefold increase and a corresponding reduction in eddy-current loss, although this is counteracted by an increase in hysteresis loss and reductions in saturation magnetostriction and d-coefficient. Examination of the microstructure suggests that improved performance would result from slight modification to the composition. Dynamic magnetomechanical properties and energy loss of the Terfenol powder composite are shown to be generally superior to those of Si-Terfenol. Eddy-current loss is reduced by a factor of about 13, compared with bulk Terfenol, although this is not as great as predicted by classical theory from the measured resistivity.