Microstructure and Tunneling Magnetoresistive Characteristics of Laser Irradiated Magnetic Data Recording Head

Heat-assisted magnetic recording is a future hard disk drive (HDD) technology for extremely increasing areal density. The tunneling magnetoresistive (TMR) device structure, located inside the magnetic read–write head of a hard drive, is the most complex and sensitive component, which contains sensitive components, such as a touchdown sensor and a near-field transducer. The laser used in the writing process might cause degradation of magnetic head components. The effects of laser irradiation on the TMR device have been investigated using a quasi-static test measurement to observe the characteristic changes of the magnetic response sensitivity function. The results showed only the amplitude degradation, as the resistance and asymmetry parameters were unchanged. The nanostructure of the degradation TMR devices was investigated by using scanning transmission electron microscopy and X-ray energy-dispersive spectrometry. It was found that the manganese depletion in the antiferromagnetic layer causes a nonactive zone due to the poor magnetic coupling pinning function and reduces the functioning of the HDD. The ratio of active and nonactive zone elements has a strong correlation to the amplitude degradation of individual TMR devices. The TMR structure with shorter strip height can have a higher risk of device degradation.