Influence of defects on magnetostrictive performance in Terfenol-D

Abstract

A large remanent strain has been normally observed in free-standing float zone-grown Tb0.3Dy0.7Fe2 (Terfenol-D) following the application of magnetic field or compressive stress. Such a strain is considered to be composed of two parts, leading to reversible and irreversible domain contributions to the magnetostriction, in which the irreversible part corresponds to the magnetostrictive jump effect belonging to non-180° domain wall motion, and the reversible part contributes to the slower changes of magnetostriction. With no stress applied, the specimen shows a jump field of 21 and 53 Oe for 180° and non-180° domain wall motion, respectively. The jump field, distribution width and hysteresis field for non-180° domain wall motion are all increased with increasing stress, indicating complicated interactions between magnetic domains and defects. Stacking faults are found by electron microscopy to often act as domain-wall pinning centers, and scanning probe microscopy shows specific domain configurations are formed around excess rare earth, twin boundaries, and grain boundaries due to induced stresses and demagnetization effects. The influence of such interactions on magnetostrictive performance is discussed.