PRESSURE DEPENDENCIES OF MAGNETOSTRICTIVE STRAIN AND D-COEFFICIENT INTERFENOL-D AFTER THERMAL OR MAGNETIC ANNEALING

The pressure dependence of the magnetostrictive strain coefficient, d( 33), and maximum strains in applied fields of 120 kA m(-1) have been m easured in samples of Terfenol-D before and after thermal or magnetic annealing. Application of an annealing field, H-a, parallel to the [11 1] axes which are normal to grains oriented along the [11 $$($) over b ar 2] axis, leads to an increase in d(33) of as much as 81%, with appl ied uniaxial prestresses as low as 3 MPa. The variation of optimum d(3 3) values as a function of stress applied along the [11 $$($) over bar 2] axis shows anomalous oscillations after magnetic annealing. The th ermal and magnetic effects of the annealing procedures are discussed a nd a mechanism to explain magnetic annealing is proposed.