Amorphous magnetostrictive alloy and an electronic article surveillance system employing same

US5841348A · kind A · utility

Assignee

• Vacuumschmelze GmbH & Co. KG · DE

Inventor

• Giselher Herzer · Bruchköbel, DE

Key dates

• Filing date: Jul 9, 1997
• Grant date: Nov 24, 1998
• Expiry date: Jul 9, 2017

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S148/003
• WIPO field: Control
• WIPO sector: Instruments

Abstract

A resonator for use in a marker, with a bias element which produces a bias field, in a magnetomechanical electronic article surveillance system is composed of an amorphous magnetostrictive alloy containing iron, cobalt, nickel, silicon and boron in quantities for giving the resonator a quality Q which is between about 100 and 600. The amorphous magnetostrictive alloy is annealed in a transverse magnetic field for giving it a B-H loop which is linear up to about 8 Oe and an anisotropy field strength of at least 10 Oe. When the resonator is excited to resonate by a signal emitted by the transmitter in the surveillance system, it produces a signal at a mechanical resonant frequency which can be detected by the receiver of the detection system. Due to the resonator having a quality Q in the above range, the signal produced by the resonator in a first detector window, beginning approximately 0.4 ms after excitation, has a high amplitude which is no more than 15 dB below its amplitude immediately after excitation, but drops to a level in a the second detection window, beginning approximately 6 mm after excitation, which is at least approximately 15 dB below its level in the first detecti…