The Material that changes its dimension in the magntic field, as first discovered in 1842 by James Joule, is called magnetostrictive effect. The traditional magnetostrictive material such as iron, nickel, ferrite piezoceramic etc. are of low magnetostriction. In the early 1970s, A.E Clark and coworkers discovered that rare earth binary alloys TbFe₂, DyFe₂, SmFe₂ etc. have very large magnetostriction above room temperatures however with high anisotropy which means very large field will be needed to get suturation, and this causes great difficulty in practical applications. In solving this problem, pseodobinary alloys were studied which led to the discovery of Tb_xDy_1-xFe_2-y material possessing giant magnetostriction with low anisotropy. Grain-oriented Tb_xDy_1-xFe_2-y single crystal or multicrystal materials exhibit "jump effect" which means that the magnetostriction increases drastically in the presence of prestress. From then on, the practical application of this material became possible, therefore attracting widespread attention from industry.

     By alloying the two compounds it was found that the magnetic field required to produce saturated strains were considerably reduced. The resulting alloy Tb_0.27Dy _0.73 Fe_1.95 (commercially known as Terfenol-D) is at present the most widely used magnetostrictive material. Terfenol is capable of strains as high as 1500ppm and, since the 1980's, has been a commercially available material for application in a great many fields.