NOVELTY - A magnetostrictive device includes a magnetostrictive alloy having palladium and platinum; and nickel, cobalt, and iron.    USE - The inventive magnetostrictive device, e.g. energy conversion device, smart device, highly magnetostrictive actuator or sensor, is used as a component in a hydrogen storage medium, in a catalytic reactor system, in a isotopic enrichment system, in a torque/load sensor, in a linear motor/actuator, in a system for the generation and sensing of acoustic and ultrasonic waves, or in a system for active damping and vibration/seismic isolation structures (claimed). It is useful in industries such as nuclear energy, electric power generating companies, petrochemical industries, fuel cells, automotive industries, sensor/actuator companies, or acoustic/ultrasonic equipment manufacturers.    ADVANTAGE - The invention uses (Pd, Pt) (Fe, Co, Ni) based alloys or compositions that exhibit appreciable magnetostrictive behavior which refers to reversible strains in a material in response to an applied magnetic field and changes in magnetic properties such as permeability on the application of stress.    DETAILED DESCRIPTION - A magnetostrictive device comprises a magnetostrictive alloy having palladium (Pd) and platinum (Pt); and nickel (Ni), cobalt (Co), and iron (Fe). The alloy comprises PdxNi1-x, PdxFe1-x, PdxCo1-x, PtxNi1-x, PtxFe1-x, PtxCo1-x, where x is less than 1.    INDEPENDENT CLAIMS are also included for:    (a) a catalytic reactor comprising a catalyst comprising an alloy and a system for providing a variable magnetic field to controllably vary the catalytic activity of the alloy;    (b) a hydrogen storage system comprising a catalyst comprising an alloy and a system for providing a variable magnetic field to controllably vary the solubility and diffusion properties for hydrogen of the alloy;    (c) a method for controlling or programming the solubility and diffusion behavior in an alloy comprising providing an alloy, and subjecting the alloy to a magnetic field;    (d) a method for varying the catalytic activity in a catalyst system comprising providing an alloy, and subjecting the alloy to a variable magnetic field to controllably vary its catalytic activity in response to variation in the magnetic field; and    (e) a method for storing hydrogen comprising providing a catalyst comprising an alloy and subjecting the alloy with a variable magnetic field to controllably vary the solubility and diffusion properties for hydrogen of the alloy to effect the selective variation of solubility and diffusion of hydrogen.    The magnetic field is adjusted to a strength to obtain a preselected solubility or diffusion property in the alloy.    DESCRIPTION OF DRAWING(S) - The figure shows nature of distortions in the lattices of fcc NiPd, CoPd, and FePd magnetostrictive alloys on the application of magnetic field.