magnetic stripe

A magnetic stripe card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The magnetic stripe, sometimes called a magstripe, is read by physical contact and swiping past a reading head. Magnetic stripe cards are commonly used in credit cards, identity cards, and transportation tickets. They may also contain an RFID tag, a transponder device and/or a microchip mostly used for business premises access control or electronic payment.
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Noun
1. a short strip of magnetic tape attached to a credit card or debit card; the magnetic stripe contains data that will tell a reading device who you are and what your account number is, etc.
(hypernym) magnetic tape, mag tape, tape
(part-holonym) credit card, charge card, charge plate

layer of ferromagnetic material bonded to a non-magnetic carrier, usually plastic, as in credit cards.