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Baseline popping noise (BLPN) is characterized by the spurious popping of baseline between readback pulses from magnetoresistive/giant MR (MR/GMR) heads. This article focuses on experimental investigation of BLPN from hard-magnet-biased GMR head. It is found that BLPN is sensitive to read bias current in both magnitude and polarity. Also, we found that BLPN is very sensitive to head offset across a written track as a result of interaction between localized BLPN active slice and written track edge. Full-track and microtrack profiling of BLPN is used to substantiate these behaviors. A close-fit model is proposed to further explain the BLPN mechanism. With this model, GMR BLPN is explained by longitudinal hard bias insufficiency on a free layer. When hard bias is not strong enough, due to the demagnetization field, magnetization around edge area rotates either up or down. This skewed magnetization is not stable, a small field will make it flip up and down, which results in jumps in transfer curve and eventually instability in track average amplitude.

The work-function change of potassium on the Cu(111) surface was studied. The work-function change was measured by a Kelvin probe. The coverage of potassium on the surface was determined by AES. Maximum work-function change Δφmax=3.14 eV. Initial dipole moment p(0) = 7.0 Debye, The minimum work-function occurs at the coverage θmin= 0.18. The result of this work is consistent with that of the jellium-slab model.

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