Stable ultrahigh-density magneto-optical recordings using introduced linear defects

Abstract

The stability of data bits in magnetic recording media1,2 at ultrahigh densities is compromised by the thermal 'flips' - magnetic spin reversals - of nano-sized spin domains3, which erase the stored information. Media that are magnetized perpendicular to the plane of the film, such as ultrathin cobalt films or multilayered structures4,5, are more stable against thermal self-erasure2,6 than conventional memory devices. In this context, magneto-optical memories seem particularly promising for ultra-highdensity recording on portable disks, and bit densities of ∼100 Gbit inch-2 (ref. 7) have been demonstrated using recent advances in the bit writing and reading techniques7-11. But the roughness and mobility of the magnetic domain walls12,13 prevents closer packing of the magnetic bits, and therefore presents a challenge to reaching even higher bit densities. Here we report that the strain imposed by a linear defect in a magnetic thin film can smooth rough domain walls over regions hundreds of micrometres in size, and halt their motion. A scaling analysis of this process, based on the generic physics of disorder-controlled elastic lines14-17, points to a simple way by which magnetic media might be prepared that can store data at densities in excess of 1 Tbit inch-2.