Quantum limit of magnetic recording density

Macroscopic quantum tunneling imposes an upper limit on the areal density of magnetic disk drives. We derive a general expression for this limit, and apply it to Co-alloy-based longitudinally recorded media, as well as to potential future media based on the high anisotropy material FePt. We estimate the temperature at which the switching rate due to quantum tunneling becomes comparable to the thermally activated switching rate. This is the lowest temperature to which a magnetic storage device can be cooled with the expectation of increasing the areal density by enhancing stability against spontaneous switching. (C) 2001 American Institute of Physics.