Thin film head characteristics studied by inductance change from bias current control

Head inductance change by controlling DC bias current (L-IDC characteristics) have been studied under different frequency and ambient temperature conditions for sets of thin-film heads (TFHs) with fixed overwrite (O/W) modulation values and fixed noise probability in the write relaxation process (WRP). A good correlation between O/W values and the drop-off current value of the L-IDC curves of the TFHs also showed a good correlation with probability of the WRP noise. The ratio of the two values was roughly one noise per 1000 ripples. The fluctuation of the inductance for the TFH having WRP noise probability of less than 2×10^-4 (sample A) was 0.51 nH at 23°C and 0.91 nH at 140°C in RMS, and the head having the probability of 1.6×10^-2 (sample B) was 2.95 nH and 1.68 nH at each temperature, respectively. Sample B showed a layer temperature dependence of inductance measured at 1 MHz and at 20 MHz compared to that of the sample A. The results indicate that the WRP noise phenomena are related to the domain structure of the head yokes