This paper presents the results of an extensive series of experiments conducted on
FePd
using a recently developed apparatus, the Magneto-Mechanical Testing Machine. These
experiments were designed to investigate the ferromagnetic shape-memory behavior of
FePd
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
FePd
single crystal lengthens when a magnetic field is applied along its
axis
(short axis of FCT lattice) while the specimen is under uniaxial compression in the
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
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
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
J/m.
This work output is very close to the work output of Terfenol-D under this amount of
compressive stress.
