#### Vol. 2, No. 3, 2007

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Ferromagnetic shape memory effects in an iron palladium alloy

### Jun Cui and Tom Shield

Vol. 2 (2007), No. 3, 505–528
##### Abstract

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 $9.6×1{0}^{3}$ J/m${}^{3}$. This work output is very close to the work output of Terfenol-D under this amount of compressive stress.

##### Keywords
ferromagnetic shape memory, FePd, iron-palladium alloy