Magnetostrictive properties of polymer-bonded amorpnous Tb-Fe-B composites

Amorphous ribbons of an alloy with the composition (Tb _0.33Fe_0.67)_0.98B_0.02, which exhibit good magnetostrictive properties at low magnetic fields, are bonded with a phenol-based binder to fabricate bulk composites. Efforts to determine optimum fabrication parameters are made by examining magnetic and mechanical properties of bulk compacts obtained at various fabrication conditions. From the binder content dependence of magnetostriction and compressive strength, the optimum binder content is estimated to be about 4.3 wt %, taking into account magnetostrictive and mechanical properties and the necessity of reducing nonmagnetic binder content. The two properties of magnetostriction and compressive strength vary nearly linearly with the compaction pressure; as the compaction pressure varies from 0.25 to 1.0 GPa, magnetostriction decreases but compressive strength increases, making it difficult to determine the optimum compaction pressure. A magnetostriction of 493 ppm (at 1.1 kOe) is achieved from the present bulk composites, together with a high dλ/dH (sensitivity of magnetostriction with applied magnetic field) of 1 ppm/Oe.