Measuring the gigahertz response of recording heads with the magnetic force microscope

We compare two different techniques for measuring the high frequency response of recording heads using a magnetic force microscope. The first technique is based on driving the recording head with a high frequency current. We separated the high and low frequency response of the recording head by making two measurements, one with the current on, one with the current off. The second technique is based on amplitude modulation of the high frequency current driving the recording head. This technique has the advantage of separating the low and high frequency response in a single measurement. We used both of these techniques to study the spatially dependent response of recording heads operating up to and beyond 1 GHz. (C) 1999 American Institute of Physics. [S0003-6951(99)01209-7].