Control of Coercivities in (Ga,Mn)As Thin Films by Small Concentrations   of MnAs Nanoclusters
  We demonstrate that low concentrations of a secondary magnetic phase in (Ga,Mn)As thin films can enhance the coercivity by factors up to ~100 without significantly degrading the Curie temperature or saturation magnetisation. Magnetic measurements indicate that the secondary phase consists of MnAs nanoclusters, of average size ~7nm. This approach to controlling the coercivity while maintaining high Curie temperature, may be important for realizing ferromagnetic semiconductor based devices. 
K. Y. Wang, M. Sawicki, K. W. Edmonds, R. P. Campion, A. W. Rushforth,   A. A. Freeman, C. T. Foxon, B. L. Gallagher, and T....