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

Abstract

The stability of data bits in magnetic recording media^1,2 at ultra-high 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 structures^4,5, are more stable against thermal self-erasure^2,6 than conventional memory devices. In this context, magneto-optical memories seem particularly promising for ultrahigh-density 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 techniques^7,8,9,10,11. But the roughness and mobility of the magnetic domain walls^12,13 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 lines^14,15,16,17, 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.