Antenna core and a manufacturing method thereof, and antenna and detecting system using the same

Antenna core comprises a laminate of a plurality of Co-based amorphous magnetic alloy thin ribbons ratio of the length of the long axis to the length of the minor axis is greater than 1. Co-based amorphous magnetic alloy thin ribbons 60% or more the number ratio of the plurality of Co-based amorphous magnetic alloy ribbon 1 has a line-shaped marks 2A formed along the longitudinal axis on at least one surface. Antenna includes a winding wound along its long axis and antenna core.