An improved output magnetoresistance effect type head having a spin valve type multilayered film which includes a non-magnetic metal layer, a ferromagnetic layer, a soft magnetic layer, and a pinning layer, where the soft magnetic bias assist layers formed on the soft magnetic layer changes its magnetization direction in an external magnetic field. On the basis of the regular data, a real-time indication of the quality of service is calculated in a first process. The electromagnetic device applies a torque to the spindle in response to the measurement to change the speed of the spindle to the desired speed.