Magnetostriction of Polycrystalline Tb-Dy Alloys at Cryogenic Temperatures

Single crystals of Tb-Dy alloys exhibit magnetostrictive strains and forces sufficiently large to make them useful as actuators in cryogenic mechanical devices. These actuators offer many advantages over piezoelectric actuators and actuators using motion feedthroughs from higher temperature. We are developing textured polycrystalline materials as alternatives to single crystals, since polycrystals are much simpler to prepare and are less costly. Magnetostrictive strains of 56% of the single crystal value are reported for deformation-processed Tb-Dy. We show that substantial magnetostriction can be attained using low cost commercial grade (total purity 99.7%) Tb-Dy material (as opposed to expensive high purity (99.94%) material required for the growth of single crystals). The effect of grain size and texture on magnetostrictive performance is discussed