Magnetomechanical behaviour of rare earth iron-aluminium compounds

The DC field and pressure dependencies of the magnetic induction (B) and magnetostrictive strain ( lambda ) have been measured at room temperature in Terfenol-D (Tb/sub 0.3/Dy/sub 0.7/Fe/sub 1.95/) and in the compound Tb/sub 0.3/Dy/sub 0.7/(Fe/sub 0.9/ Al/sub 0.1/)/sub 1.95/. From these data the static differential permeability ( mu ) and strain coefficient (d/sub 33/=d lambda /dH) have been obtained. A comparison of their magnetostrictive responses indicates that the magnetocrystalline anisotropy is reduced by the addition of Al to Terfenol-D. A slight lowering of d/sub 33/ with Al content is attributed to a reduction in magnetoelastic coupling, also seen in a lower magnetomechanical coupling coefficient. The work done by either compound against the applied pressure for different isostatic fields has been calculated. From these curves the residual stress levels, T/sub 0/, are substantially lower than those reported previously in Tb/sub 0.27/Dy/sub 0.73/Fe/sub 2/, indicating that in the present compounds T/sub 0/ is due mainly to inhomogeneities and defects, rather than anisotropy.<
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