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

Abstract

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 highresolution MR sensors from commercial hard disk drives. These images can be directly converted into the originally recorded analog audio waveforms or digital data.

Multichannel real-time magnetic imaging system

“…We recently designed and fabricated a novel alternative to this technique that is noninvasive, sensitive to field polarity, shows high spatial resolution, and has the potential to make images as the tape is played. 2 This new type of magnetic imaging system comprises a linear array of sensors on a die (see Figure 1) that connects the signals from 256 sensor channels to custom, low-noise electronics for imaging and readout. The tape to be analyzed is brought to within a few microns of the sensor array by a transport system and is continuously run past the sensor stripe, also known as the read head, in the same fashion as a traditional tape in a cassette player.…”