At least as of the last time I read the domains were a pretty uncontrolled result of the crystalization and each bit is covering a few statistically. Nanopatter

At least as of the last time I read the domains were a pretty uncontrolled result of the crystalization and each bit is covering a few statistically. Nanopatterning of the sort your describing would let you make the bits smaller and hence weaker by ensuring a separation and friendlier magnetic environment.