For nearly 50 years, Terfenol-D (Tb:x:Dy:1-:x:Fe:2:) has reigned as the material for which an applied magnetic field results in the greatest change in shape, a property known as magnetostriction. A distant second to Terfenol-D is Galfenol (Fe:1–:x:Ga:x:), the best magnetostrictor free of rare-earth elements.