Interaction fields and media noise in CoPtCr thin films

Remanence measurements have been made on a series of CoPtCr thin films of varying composition in order to correlate the interaction field with media noise. δM versus h curves have been analyzed using a phenomenological model of Che and Bertram, in which the interaction field is given by h_int=αM_R+β(1-M_R ²), where M_R=M_r (or M_d). We have shown analytically that α and β can be simply determined respectively from the area under the δM versus h curve (or δh versus M_R) and the zero crossing of the curve. The parameter β, which is related to the strength of the fluctuation field, was found to increase with increasing reverse dc erase noise (measured at zero remanence). Surprisingly, perhaps, no correlation was found between this noise and α. By contrast, α, which characterizes the strength of the magnetostatic and/or exchange interaction, was positive for all samples and decreased with increasing dc erase noise (measured at saturation remanence). As expected, α was also found to increase with the magnetic viscosity, S, and to decrease as the coercivity, H_c, increased