The design of media for ultrahigh-density perpendicular recording is discussed in depth. Analytical and semianalytical models are developed to determine the constraints upon the media to fulfill requirements of writability and thermal stability, and the effect of intergranular exchange coupling is examined. The role of vector fields during the write process is examined, and it is shown that one-dimensional models of perpendicular recording have significant deficiencies. A micromagnetic model is described and the results of simulations of recording undertaken with the model are presented. The paper demonstrates that there is no physical reason why perpendicular recording should not be possible at or above 1 Tb/in(2)

Magnetovariation fields were recorded by the land part of the EMSLAB array, August‐September 1985. Data from two complete days and two shorter sequences, chosen for moderate magnetic activity, are here used to map induced currents, which flow preferentially in the more conductive rocks, in Washington and Oregon and adjoining areas. Fourier transform anomaly maps, induction vectors, and hypothetical event anomaly maps are used to delineate conductive structures. These include the ocean and suboceanic asthenosphere and extended regions of attenuated vertical component caused by highly conductive layers under the Basin and Range Province and the Canadian Cordillera, both considered associated with partial melting and hydrothermal water. The Cascade Range of volcanoes has a north‐south strip of high conductivity some 100 km wide beneath it, which is named the Deep Cascades conductor. Between 46° and 47°N the Deep Cascades currents appear to flow up through a narrow upper crustal conductor, well known from prior work by others, into Puget Sound. The Deep Cascades conductor correlates with high heat flow and probably delineates the partial melting beneath the volcanic arc. At its southern end it appears to be continuous with the Basin and Range regional conductor. Northward it terminates between 47.5° and 48°N, south of Mounts Baker and Garibaldi. The Blue Mountains of NE Oregon and SE Washington coincide approximately with a kidney‐shaped block of resistive lithosphere, which lies between the Klamath‐Blue Mountain Lineament and the conductive mantle of the Basin and Range. The Columbia Embayment and plateau basalts occupy a triangular block of lithosphere more resistive than the Canadian Cordilleran Regional Conductor, which abuts against it, but less resistive than the Blue Mountains. Boundaries between these tectonic units are mapped from the associated magnetovariation anomalies, that is, in terms of electrical conductivity.

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The design of media for ultrahigh-density perpendicular recording is discussed in depth. Analytical and semianalytical models are developed to determine the constraints upon the media to fulfill requirements of writability and thermal stability, and the effect of intergranular exchange coupling is examined. The role of vector fields during the write process is examined, and it is shown that one-dimensional models of perpendicular recording have significant deficiencies. A micromagnetic model is described and the results of simulations of recording undertaken with the model are presented. The paper demonstrates that there is no physical reason why perpendicular recording should not be possible at or above 1 Tb/in 2 .

No abstract