First, we examined the sensitivity of the head to a high
frequency signal field. The Hslg dependence of the output
voltage (V,,) is shown in Fig. 3. Hsig with a signal
fkequency (fsig) of 5 MHz was applied using a solenoid coil.
In order to provide linearity, we used a Helmholtz coil to
apply an appropriate constant dc bias field. A carrier power
(Pear) of 15 dBmwas set with an fear of 735 MHz. VOut
was normalized with the core width (w,). Both V, and
Hsig m root mean square values. A sensitivity of 4 mV/pm*
Qe was maintained linearly below an Hsig of 0.3-0.4 Oe.