Magnetostriction ‘‘jumps’’ in twinned Tb0.3Dy0.7Fe1.9

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Abstract
Large ‘‘jumps’’ in the magnetostriction have been observed in twinned single crystals of Tb0.3Dy0.7Fe1.9 (Terfenol‐D) for magnetic fields parallel to the crystalline [112̄] direction. The interpretation of these large magnetostriction discontinuities is based upon a model of twinned dendritic Terfenol‐D in which the magnetization of one twin jumps between two [111] directions while the magnetization of the remaining twin undergoes a continuous rotation of the magnetization. The field dependence of the magnetization and magnetostriction of cubic single crystals with λ111≫λ100 was calculated using an expression which included the anisotropy constants K1 and K2 and compressive loads along [112̄]. With K1=−0.6 J/m3 and K2=−2.0 J/m3 (values appropriate for Terfenol‐D near room temperature), magnetization ‘‘jumping’’ is predicted. For the twinned crystal, the jump in the magnetostriction was calculated to be greater than 1000 ppm. Because of this large magnetostriction, it is possible to configure a device to perform a substantial amount of work by the application of only a triggering magnetic field centered about an optimum bias field.

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