Dipole-dipole interaction in electronic article surveillance system

The dipole-dipole interaction in electronic article surveillance system is studied in this paper. The acoustic magnetic properties investigations were performed on amorphous ribbon Fe₂₄Co_11.82Ni_47.3Si_1.47B₁₅ with a size of 38.5 mm × 6 mm ×0.03 mm at room temperature. The results showed that the dependence of resonance amplitude and frequency on the external magnetic field varied with the number of ribbons. To understand the mechanism, hysteresis loops in arrays of N ribbons with and without a bias magnet have been performed. A theoretical model was used to calculate the dipolar fields among the ribbons and the magnet. The ribbons without a bias magnet exhibited a higher anisotropy field as the number of ribbons increased, which arises from the dipole-dipole interaction between them. The plateau and kink in hysteresis loops with bias magnets also change with the number of ribbons because of the dipole-dipole interactions among the ribbons themselves, and the interaction between the ribbons and the bias magnet also. The superimposed dipolar field affects the acoustic magnetic properties of the ribbons in electronic article surveillance system.