Ferromagnetic shape memory effects in an iron palladium alloy

This paper presents the results of an extensive series of experiments conducted on Fe 70 Pd 30 using a recently developed apparatus, the Magneto-Mechanical Testing Machine.These experiments were designed to investigate the ferromagnetic shape-memory behavior of Fe 70 Pd 30 and test the predictions of a theory that assumes the magnetizations of the material are constrained to lie in the easy directions and the material strains are constrained to be the shape-memory transformation strains.It was found that a specimen made of Fe 70 Pd 30 single crystal lengthens when a magnetic field is applied along its c axis (short axis of FCT lattice) while the specimen is under uniaxial compression in the c direction.This behavior agrees with the predictions of the constrained theory and magnetic anisotropy measurements.The maximum field-induced strain change measured in this material is about 0.009 at 5500 G and -1 MPa, which is one fifth of the theoretical prediction.This is attributed to the magnetization rotation away from the easy directions caused by insufficient magnetic anisotropy.Under -12 MPa of compression the field-induced strain change is considerably smaller reaching only about 0.0008, but this change gives the largest work output observed of 9.6 × 10 3 J/m 3 .This work output is very close to the work output of Terfenol-D under this amount of compressive stress.