Estimation of Critical Current Density of Spin-Torque Noise in Tunneling Magnetoresistive Read Heads with Varying Stripe Heights

摘要

The continued increase in the areal density of a magnetic recording media has required minutiarization of read heads down to approximately 20 nm, the signal-to-noise ratio (SNR) of read-out data for the heads is accordingly markedly degraded by thermally excited magnetization fluctuation noise (thermal mag-noise) and non-thermal fluctuation noise from spin-torque (ST). Non-thermal fluctuation noise, in particular, is a serious issue for tunneling magnetoresistive (TMR) read heads; ST influences the thermal mag-noise below the critical current density j_c, and leads to a steady state precession above j_c in the TMR head. Therefore it is crucial to understand ST in detail.