Second-harmonic magnetoresistive imaging to authenticate and recover data from magnetic storage media

A scanning magnetoresistive (MR) microscope is developed for high-resolution imaging of magnetic tapes and digital media. Second-harmonic detection is used to remove thermal anomalies. We are able to image sufficient lengths of tape for authentication purposes and for data recovery from damaged samples. The second-harmonic technique provides high-contrast magnetic images of the magnetic storage media using high-resolution MR sensors from commercial hard disk drives. These images can be directly converted into the originally recorded analog audio waveforms or digital data.