Real-Time Measurement of Temporal Response of a Spin-Torque Oscillator to Magnetic Pulses

A read head based on a spin-torque oscillator (STO) has been proposed for the high-density magnetic recording beyond 2 Tbit/in.(2). To evaluate the stability and agility of the oscillation, we conduct a real-time measurement of the STO waveform under a magnetic pulse (similar to 60 Oe) in the nanosecond region, and estimate its instantaneous frequency. Stable oscillation is sustained in the presence of the magnetic pulse, and the frequency shift is clearly observed, indicating that the STO frequency responds to the change in magnetic field in less than 1 ns. (C) 2011 The Japan Society of Applied Physics