Spin-Torque Oscillator Read Head in Inhomogeneous Magnetic Fields

Spin-torque oscillators (STOs) are the candidates for a novel class of magnetic field sensors, suitable especially for magnetic media read head purposes. While a number of investigations on the STO readout ability have been reported, comparatively little attention has been paid to the issue of its behavior in highly inhomogeneous magnetic fields, i.e., generated by densely stored magnetic media. We examine the theoretical limits for the STO technology usage for sensor applications, using both a general auto-oscillator model and a micromagnetic simulations framework. We find that the deterioration of the output signal may lead to significant readout errors already for the bit width of a few nanometers, which is close to the current state-of-the-art in the data storage industry.