Influence of polarity of media DC background on write/read performance in perpendicular media with an antiferromagnetically stabilized soft underlayer

A recording system which consists of a double layer recording medium with an antiferromagnetically (AFM) stabilized soft underlayer (SUL), a single pole writer, and a conventional reader, has been studied with respect to the symmetry and amplitude of the dibit pattern, as a function of the dc-erased background polarity. While dibit asymmetry contains both readback effects, due to read head nonlinearity, and write effects due to transition shift, the effect of dc background polarity on asymmetry appears to be exclusively a readback phenomenon. Measurements of isolated transitions indicate neighborhood induced transition shift from writing is actually a more significant contributor to dibit asymmetry than the reader bias shift during reading. Finally, the presence of the AFM layer appeared to double both of these effects over unstabilized media and resulted in a pronounced impact on the recording performance. The latter observations are attributed to an increase in the effective permeability of the stabilized SUL (due to more favorable domain configurations) even though absolute SUL permeability decreases when AFM stabilization is used.