Sub-Nanosecond Switching of Spin-Transfer-Torque Device for Energy-Assisted Perpendicular Magnetic Recording

A giant magnetoresistance (GMR)-based spin-transfer-torque (STT) device is built into the top gap (TG) of the writer of a magnetic write head for energy-assisted magnetic recording. Magnetization of the spin-torque layer (STL) in the STT device can be aligned opposite to the magnetic field direction inside the TG, thus increasing the write field seen by the media. A method for high-speed, real-time measurement of the switching dynamics of the STL when the writer switches polarity is developed. We demonstrate that the switching time of STL can be 300 ps or less, we also show that STL dimensions can strongly affect the switching speed of the STL and are important design parameters that need to be optimized for performance and reliability tradeoffs. The measurement results are compared to micro-magnetic simulation. They show qualitative agreement with some discrepancies, and possible causes are discussed.