High frequency response of thin film heads by scanning Kerr effect microscopy

A scanning Kerr effect microscope (SKEM) was built that features 0.025-μm step sizes and 5° phase resolution over a 50-MHz bandwidth. Scans were made on several NiFe and CoZr thin-film recording heads with different head geometries. The measured values of head saturation are in rough agreement with those calculated from a model for saturation near the back gap. The frequency response of the NiFe heads shows that the real component of the efficiency rolls off smoothly, and the imaginary component peaks between 15 and 40 MHz. The bandwidth increases with DC efficiency and is two to three times lower than computed values. The frequency response of the CoZr head showed peaks and valleys that were attributed to a misoriented easy axis. The response of the heads studied here is most likely determined by domain behavior