A resonant RF electronic article surveillance marker includes a substrate, a coil formed on the substrate, and a capacitor formed on the substrate. The coil includes a magnetic element which exhibits a GMI effect. Two signals are employed to interrogate the marker—an RF carrier signal and a low-frequency alternating magnetic field. Because of the presence of the GMI element, the marker mixes the low frequency signal with the carrier signal to generate a sideband of the carrier signal. The sideband signal is very unique and can be detected with a high degree of reliability. The marker may also include magnetic control elements which can be magnetized to disable the marker and de-magnetized to reactivate the marker.