Terfenol-D has the highest magnetostriction of any alloy, up to 0.002 m/m at saturation.
It was initially developed in the 1970s at the Naval Ordnance Laboratory — the name joins terbium, iron and NOL, with D for dysprosium — and manufacturing was refined at Ames Laboratory in the 1980s.
Its first application was naval sonar; it now drives sensors, actuators, diesel fuel injectors and underwater transducers working to 1000 ft, and FeONIC's SoundBug was its first commercial product.