Recording Head Characterization Using a Narrow Domain Wall in Epitaxial Garnet Films

A domain wall in a ferromagnetic garnet film with high perpendicular anisotropy is used as a highly localized field source with nanometer extent. When the domain wall is moved crosstrack over the read sensor of a perpendicular recording head, the spatial response function of the sensor is measured. From the response curve, the magnetic read width of the sensor can be calculated and details of the response can reveal local sensor instabilities. By oscillating the domain wall at a frequency of a few megahertz, the method can also be applied to write-head testing when the write pole is subjected to the field from the oscillating domain wall and the induced voltage in the write coil is measured.