The effect of composition and magnetic heat treatment on the magnetostriction of Tb/sub x/Dy/sub 1-x/Fe/sub y/ twinned single crystals

Twinned single crystals of the giant magnetostrictive intermetallic compound Tb/sub x/Dy/sub 1-x/Fe/sub y/ with a <112> axial alignment have been prepared by float-zone solidification with Y varying from 1.90 to 1.98 and X being 0.32 or 0.28. The chemical compositions of the crystals were carefully analyzed. A very sharp jump in the magnetostrictive strain λ sometimes occurs in these alloys as the applied field H is increased to values of around 280 Oe under a compressive stress of 6.9 MPa. This large jump in λ is shown to depend strongly on the values of X and Y, and possible reasons for this result are discussed. A magnetic heat treatment has been developed which involves cooling the samples through the Curie temperature under a field applied transverse to the crystal axis. It is shown that this treatment is very effective at increasing the magnetostrictive properties at low applied compressive stresses for certain values of X and Y