Influence of Stripe Height on Critical Current Density of Spin-Torque Noise in Tunneling Magnetoresistive Read Heads

This paper describes the influence of the stripe height on the critical current density of the spin-torque (ST) noise in the TMR heads using the GHz range noise spectra in detail. The critical current density above which the non-thermal fluctuation noise originates from the ST slightly increases, linearly decreases, becomes minimum, and further keeps constant as the stripe height is reduced. This result means that no trend of j_c appears for the stripe height. The average critical current density is approximately +4.70 ± 1.1 × 10¹¹ A/m², suggesting that the non-thermal fluctuation noise by the ST in the TMR head is independent of the stripe height and occurs at the current density of 10¹¹ A/m². This result also suggests that this non-thermal fluctuation noise will become a serious problem for the HDD in the near future.