Magnetization Canting in Synthetic Read Heads at Ultrahigh Recording Density

In this paper, we study the magnetization canting of the free layer in a synthetic spin valve at ultrahigh density data recording up to 10 Tb/in². Our micromagnetic simulations show that the canting problem deteriorates dramatically as the sensor size shrinks further to match higher data-recording density. Our systematic investigation on the magnetic field distribution reveals that the increasing net magnetostatic coupling field from the synthetic antiferromagnet (SAF) at smaller sensor dimensions is responsible for the observed effect. Further studies show that the stray field experienced by the free layer was dominated by the reference layer, and both the field profile and magnitude change markedly with the closer proximity of the magnetic charges. In order to restore the sensor to the appropriate operating point, affects of adjusting the thickness and magnetization ratio in the SAF, and tapering angle of the sensor stack, have been investigated and it was found that they were able to relieve the canting problem to certain extent. The findings in this work help to optimize the sensor properties for ultrahigh density data storage in the hard disk.