Anisotropic perpendicular axis magnetostriction in twinned TbxDy1−xFe1.95

Abstract

The longitudinal magnetostriction (Δl/l) for twinned Tb x Dy1−x Fe1.95material, prepared by the free‐standing float‐zone method, has been previously measured and found to be very large (2000×10−6) at room temperature. The magnetostrictions for the [111] and [11̄0] crystallographic axes perpendicular to the applied stress and magnetic‐field [112̄] direction are presented as functions of temperature, applied stress, and applied magnetic field. The temperature range is ±60 °C centered about the anisotropy compensation temperature of Terfenol‐D (+10 °C). The stress ranges from 2 to 32 MPa and the magnetic field to ±2000 Oe. The temperature dependence of the perpendicular axes magnetostriction is similar to that of the conventional magnetostriction measured parallel to the [112̄] growth axis. Relative values for the saturationmagnetostriction exhibit a large anisotropy in the perpendicular direction, ranging from −117% for the [111] to +19% for the [11̄0] direction. This ratio stays constant as a function of temperature above the compensation temperature for a given prestress above 8 MPa. The largest absolute value of magnetostriction (2260×10−6) occurs in the [111] direction at 10 °C at a prestress pressure of 12 MPa. Above this temperature the magnetostriction falls at a rate of −8.5×10−6/°C. The volume magnetostriction is shown to be small and highly sample dependent. All data is consistent with the parent‐twin magnetization model and also the magnetostriction values along nonprincipal axes.