APPLICATIONS OF AMORPHOUS WIRE

In-water-quenched amorphous magnetic metal wire has been available for a decade. In this time, the unique properties of the wire have create d many new uses, especially in the field of electronic devices and sen sors. Because of the near-ideal mechanical properties of amorphous met al, the wire can be die drawn to various wire diameters which can be m uch smaller than is possible with polycrystalline magnetic materials. Diameters of any value from the as-cast value of about 135 mum down to 10 mum are available. Also the wire can be used in applications where mechanical strength as well as unique magnetic characteristics are ne eded. Since magnetic metals are typically magnetostrictive, changing t he chemical composition of the amorphous wire can be used to change th e magnetostriction which, in combination with residual or applied stre ss, provides yet another opportunity to tailor the magnetic character to the device needs. Flux reversal lies at the heart of all electronic devices since the ultimate output is always a voltage to interact wit h the other electronic elements. Wire can have a longitudinal flux cha nge or a circumferential flux change or a combination of two. The most curious, although not necessarily the most useful, is the re-entrant longitudinal reversal found in magnetostrictive as-cast and die-drawn tension-annealed wire. Re-entrant reversal takes the same time and hen ce generates the same voltage, essentially independent of the drive fi eld amplitude or frequency within the range of electromechanical devic es. It is useful for tachometers where the frequency changes or securi ty sensors where the drive field changes over a wide range. Since the reversal mechanism involves a magnetic domain wall propagating along t he wire, distance sensors are also possible. By twisting the magnetost rictive wire, the longitudinal flux can be coupled to the circumferent ial flux which links the wire itself. This Matteucci effect allows the sensor to be driven or the output voltage observed between each end o f the wire, providing a great convenience and flexibility for some typ es of devices. The ability to drive the reversal using a current throu gh the wire is also popular with non-magnetostrictive wires. Here, the sharp and predictable demagnetizing effects resulting from the wire g eometry make the wire attractive for electronic device applications su ch as the data tablet, miniature chokes and transformers.