Pressure dependencies of magnetostrictive strain and <i>d</i> coefficient in Terfenol-D after thermal or magnetic annealing

Abstract

The pressure dependence of the magnetostrictive strain coefficient, d33, and maximum strains in applied fields of 120 kA m−1 have been measured in samples of Terfenol-D before and after thermal or magnetic annealing. Application of an annealing field, Ha, parallel to the 〈111〉 axes which are normal to grains oriented along the [112̄] axis, leads to an increase in d33 of as much as 81%, with applied uniaxial prestresses as low as 3 MPa. The variation of optimum d33 values as a function of stress applied along the [112̄] axis shows anomalous oscillations after magnetic annealing. The thermal and magnetic effects of the annealing procedures are discussed and a mechanism to explain magnetic annealing is proposed.