Wiegand effect [SEP] named after
Wiegand effect
The Wiegand effect is a nonlinear magnetic effect, named after its discoverer John R. Wiegand, produced in specially annealed and hardened wire called Wiegand wire.
Wiegand wire is low-carbon Vicalloy, a ferromagnetic alloy of cobalt, iron, and vanadium. Initially, the wire is fully annealed. In this state the alloy is "soft" in the magnetic sense; that is, it is attracted to magnets and so magnetic field lines will divert preferentially into the metal, but the metal retains only a very
has flipped magnetization, it will retain that magnetization until flipped in the other direction. Sensors and mechanisms that use the Wiegand effect must take this retention into account.
The Wiegand effect is a macroscopic extension of the Barkhausen effect, as the special treatment of the Wiegand wire causes the wire to act macroscopically as a single large magnetic domain. The numerous small high-coercivity domains in the Wiegand wire outer shell switch in an avalanche, generating the Wiegand effect's rapid magnetic field change.
Applications.
Applications Wiegand keycards.