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The characteristics of exchange-biased soft underlayers (SULs) were investigated using magnetic force microscopy and spin stand measurements with a single-pole (focused ion-beam trimmed gap) writer and magnetoresistive head. The SUL high-moment materials (FeCoB, FeAlN) were exchange biased by using IrMn. Spin stand data on perpendicular media (CoCrPtB) with an exchange-biased FeCoB SUL also showed a low integrated dc erase noise level, demonstrating its potential for use in double-layered perpendicular media. Index Terms--Exchange biasing, media noise, perpendicular media, soft underlayers.

We discuss a method for the determination of activation volumes of reversal in perpendicular media. This method does not require correction for the self-demagnetizing field normally associated with these media. This is achieved by performing time dependence measurements at a constant level of magnetization. From the difference in time taken for the magnetization to decay to a fixed value at two fields separated by a small increment [DELTA]H, the activation volume can be determined. We report data for both CoCrPt alloy films and a multilayer film, typical of those materials under consideration for use as perpendicular media. We find activation volumes that are consistent with the hysteresis curves of the materials. The activation volume scales qualitatively with the exchange coupling. The alloy films have significantly lower activation volumes, implying that they would be capable of supporting a higher data density. Index Terms--Activation volume, fluctuation field, magnetic characterization, perpendicular recording media.

The inclusion of a An layer in the magnetic tunnel junction structure Fe/MgO/CoFe substantially alters the magnetic properties. In this work we use zero field 59Co NMR to see if these changes in magnetic properties are correlated with changes in the local atomic environment. The technique of spin-echo NMR allows the effective magnetic field (hyperfine field) at the nucleus to be determined and so provides information on the local atomic environments including strain effects and magnetic moments. The results show that the local atomic environment of Co does not change significantly, however the r.f. power required to obtain the maximum signal is substantially different when the Au layer is included showing that the r.f. electronic enhancement factor changes appreciably. Index Terms - Magnetic tunnel junctions, NMR, Thin films.