Locating magnetic noise sources in TMR and GMR recording heads using scanning probe microscopy

A scanning magnetic microscope was designed and built to pinpoint the location of magnetic noise induced by magnetic instabilities in submicrometer-sized giant magnetoresistive (GMR) and tunneling magnetoresistive (TMR) recording heads. A scanning nanometer-sized magnetic tip was used to generate a localized magnetic field and excite the free-layer magnetic moment at the air-bearing surface (ABS). The spectral response of the GMR and TMR recording heads is due to this localized oscillating excitation and is recorded as a function of the tip location. By mapping out the magnetic noise as a function of position, the trouble spots that indicate magnetic instabilities inside the recording head are identified.