Wiegand wire

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Wiegand wire is produced by cold-working a 0.010 inch (1 millimeter) diameter ferromagnetic wire made of Vicalloy, a mixture of cobalt, iron, and vanadium. The cold-working process consists of increasing amounts of twist and de-twist of the wire under applied tension in several steps. The wire is then age-hardened to hold in the tension built up during the cold-working process. This procedure causes the Wiegand wire to have a soft magnetic center, the core, and a work-hardened surface with a higher magnetic coercivity, the shell. When an alternating magnetic field of proper strength is applied to the Wiegand wire, the core's magnetic field will switch polarity and then reverse again, causing a Wiegand pulse to be generated. This is called the Wiegand effect.

The patented cold-working process that produces the Wiegand wire permanently locks in the ability to exhibit Barkhausen jump discontinuities in the material. To achieve magnetic switching, the wire is put in the presence of alternating longitudinal magnetic fields. The resultant hysteresis loop contains large discontinuous jumps known as Barkhausen discontinuities that occur due to shell and core polarity switching.