Current-Induced Magnetization Switching in Seed Optimized Perpendicular Magnetic Tunnel Junctions with Enhanced Spin-Transfer-Torque Efficiency and Uniformity

A NiCr film is introduced in magnetic tunnel junction (MTJ) seed layer to improve the smoothness of multilayer and to enhance the perpendicular magnetic anisotropy (PMA) of the pinning layer. Especially motived by the better uniformity of tunneling magnetoresistance (TMR) and switching current density (Jc), the superiority in endurance and data retention for less tailing bits is demonstrated. Benefiting from the higher spin-transfer-torque (STT) efficiency, higher coercivity and lower Jc were achieved at the same time, with satisfying 10 years retention at 85 °C and the endurance cycling lifetime up to at least 1010 cycles. This work establishes an effective path to improve STT efficiency and uniformity to expedite the commercial application of STT-magnetoresistive random access memory (MRAM).