Enhanced signal amplitude in acoustic-magnetomechanical eas marker

Abstract

Systems ( 100 ) and methods ( 600 ) for making a marker. The methods comprise: obtaining a resonator material which has been annealed under a tensile force selected to provide a maximum resonant amplitude at a bias field H max in the marker; and providing with the bias material of the marker an operating bias field H operating with a value less than a value of said bias field H max . The value of H operating is reduced by performing at least one of the following operations: selectively modifying a geometry of a bias material which is to be disposed in a housing of the marker; selectively modifying a spacing between the resonator material and the bias material arranged in a stacked configuration; and partially de-gaussing the bias material subsequent to being fully saturated.

We claim: 
     
         1 . A marker, comprising:
 a resonator material having a chemical composition of Fe a Co b Ni c Si d B e , wherein a, b, c, d and e are in atomic percent and where 22≦a≦36, 10≦b≦13, 43≦c≦49, 1≦d≦4, and 15 e≦17, the resonator material having been annealed under a tensile force selected to provide a maximum resonant amplitude at a bias field H max ; and   a bias material which has been processed to provide a value of an operating bias field H operating  in said marker which is less than a value of said bias field H max .   
     
     
         2 . The marker of  claim 1 , where said bias material comprises at least one of the following features:
 a selectively modified spacing from said resonator material; and   a partially reduced remanent magnetic field which was obtained by partially degaussing the bias material prior to when the marker is attached to an articular to be protected or tracked.   
     
     
         3 . The marker of  claim 1 , wherein the resonator material is annealed subsequent to a rapid magnetic quenching of the material at a temperature between 340° C. and 400° C. 
     
     
         4 . The marker of  claim 3 , wherein the resonator material is anneals for a time interval lasting between 5 to 30 seconds. 
     
     
         5 . The marker of  claim 1 , wherein bias field H MAX  is between 6.5 and 7.7 Oe, and the anisotropy field H k  for the resonator material is between 8 and 9 Oe.