Pinning a Domain Wall in (Ga,Mn)As with Focused Ion Beam Lithography
  We utilize a focused beam of Ga+ ions to define magnetization pinning sites in a ferromagnetic epilayer of (Ga,Mn)As. The nonmagnetic defects locally increase the magneto-crystalline anisotropy energies, by which a domain wall is pinned at a given position. We demonstrate techniques for manipulating domain walls at these pinning sites as probed with the giant planar Hall effect (GPHE). By varying the magnetic field angle relative to the crystal axes, an upper limit is placed on the local effective anisotropy energy. 
A. W. Holleitner, H. Knotz, R. C. Myers, A. C. Gossard and D. D.   Awschalom