Modeling of magnetic thermal noise in stable magnetic sensors

Low-frequency noise is a critical issue in magnetic tunneling read sensors. In this work, a mechanism of low-frequency noise generation due to asymmetric oscillations is analyzed using the Langevin equation applying both biharmonic and approximated skew normal distribution energy potentials. Both models show a high degree of correlation between low-frequency noise and fluctuations of resonance oscillation amplitude only when oscillation asymmetry is present. Furthermore, the low-frequency spectrum approaches a 1/fα profile as asymmetry increases. To investigate the effect of asymmetry in magnetic read sensors, a macrospin model was developed and validated by comparison with a full micromagnetic simulation. This macrospin model was used to study low-frequency noise by introducing asymmetry via shape anisotropy of the reader. The presence of this effect of low-frequency noise generation in reader devices is confirmed with this model, and its effect with varying temperature and damping constant is investigated.