Current-perpendicular-to-plane multilayer sensors for magnetic recording

We investigated current-perpendicular-to-plane giant magnetoresistance multilayer (CPP-ML) sensors with an active region of (1.0-nm CoFe/1.8-nm Cu) × 15 nm. These sensors would allow a shield-to-shield spacing of less than 50 nm. Square CPP-ML devices ranging in size from 120 to 365 nm on a side have been fabricated and tested. In this paper, we focus on the magnetotransport properties of the 140 nm devices, which were measured at room temperature. The average device characteristics were found to be R_max=1.0 Ω, R_min=0.81 Ω, DR=191.1 Ω, and DR/R_min=23.7. These values were measured by using a four-point probe geometry; the data were not corrected for lead or contact resistance and no current crowding was observed. After correction for buffer and seed layer resistances, the magnetoresistance had an intrinsic DR/R_min value of 55.6%. Our measured results are in good agreement with values obtained with a simple two-current series resistance model. We demonstrate that our CPP-ML structures are viable candidates to replace current-in-plane spin valves as the next generation magnetic recording readback sensor.