BURST MAGNETOSTRICTION IN TB0.3DY0.7FE1.9

The magnetostriction and magnetic induction calculated by a continuous , anisotropic, anhysteric, magnetization model are compared with magne tostriction and magnetic induction measurements on burst and nonburst magnetostrictive Tb0.3Dy0.7Fe1.9 twinned single crystal rods. The mode l shows that the magnetostriction and permeability suppression occurri ng at low applied field is the result of the rotation,and subsequent c apture, of initial field antiparallel magnetization into field transve rse [11 (1) over bar] or [<(11)over bar>1] local magnetoelastic energy minima. The model further shows that the interval of high magnetostri ction applied field derivative, d lambda/dH, characteristic of burst m agnetostrictive material, is the result of the rotation of field trans verse [11(1) over bar] or [<(11)over bar>1] oriented magnetization int o the [111] near field magnetocrystalline minima. The occurrence of bu rst magnetostriction is therefore contingent on obtaining sufficient m agnetocrystalline anisotropy and sufficiently tight magnetization ener gy distribution in experimental Tb0.3Dy0.7Fe1.9 twinned single crystal rods so as to minimize the applied field interval over which this mag netization rotation process occurs. A final analysis shows that the pr esent model is able to correctly approximate the applied field depende nce of the burst magnetostriction response and the applied field depen dence of the simultaneous magnetostriction and permeability suppressio n with a single set of parameters for a range of constant [112] applie d compressive stresses. The model additionally exhibits approximately correct saturation magnetostrictions for a range of experimentally app lied compressive stresses. However, the model fails to match the exper imental behavior above a simultaneous d lambda/dH, permeability and fi eld hysteresis transition, located approximately 1000 microstrain from the saturation magnetostriction, The experimental transition clearly indicates a change in magnetization mechanism not accommodated by the present model. (C) 1997 American Institute of Physics.