Magnetoresistance Ratio and Resistance Area Design of CPP-MR Film for 2–5 $\hbox{Tb/in}^{2}$ Read Sensors

We estimated the current perpendicular to plane (CPP)-magnetoresistance (MR) performance target required for hard disk drives (HDDs) with areal density from 2 to 5 Tb/in
²
, considering spin transfer torque (STT) and thermal magnetic noise. It is found that the noise due to STT drastically affects the MR performance target for low resistance area (RA) film. Read elements with higher RA (around 0.1-0.3 ¿·¿m
²
) are preferable to control STT. In addition, thermal magnetic noise remained smaller than media magnetic noise for 2 Tb/in
²
while it becomes comparable to media magnetic noise for 5 Tb/in
²
, suggesting the necessity of a new method to control thermal magnetic noise.