Effect of stripe height on the critical current density of spin-torque noise in a tunneling magnetoresistive read head with a low resistance area product below 1.0 Ω μm~2

摘要

To understand the spin-torque effect on the noise in tunneling magnetoresistive (TMR) read heads, the GHz range noise spectra of TMR read heads with a narrow track width (w = 36 nm), and various stripe heights (h) are investigated as a function of the external magnetic field (H_(ex)) and dc bias current density (j). The strong noise peak intensity depends on both H_(ex) and j, indicating that the spin-torque affects the thermal mag-noise under a positive (negative) j for a positive (negative) H_(ex), regardless of h in the TMR heads. Due to the increased shape anisotropy, the critical current density (j_c), where the non-thermal fluctuation noise originates from the spin-torque, increases markedly as the head dimension is reduced, and the maximum value of j_c is approximately +1.5 × 10~(12) A/m~2 for a head with w = 36 nm and h = 15 nm. These results demonstrate that the non-thermal fluctuation noise originating from the spin-torque in the TMR head can be suppressed in the current density range below 10~(12) A/m~2, as the head dimension is reduced and the shape anisotropy is increased.