Magnetic properties of MnAs nanoclusters embedded in a GaAs semiconductor matrix

We have clarified fundamental magnetic properties of MnAs nanoclusters ( 10nm in diameter) embedded in a thin GaAs matrix ( referred to as GaAs: MnAs) through tunneling magnetoresistance ( TMR) characteristics of magnetic tunnel junctions ( MTJs) consisting of a GaAs: MnAs thin film and a MnAs metal thin film as ferromagnetic electrodes. Although MnAs nanoclusters have coercive forces as small as 150 Oe at 7K, they show unusually high blocking temperature, which is as large as 300 K. The remanent magnetization of the MnAs nanocluster system linearly decreases with increasing temperature. Those magnetic behaviors cannot be explained by the non-interacting particle model, revealing the important existence of dipolar interactions in MnAs nanocluster system. (c) 2006 Elsevier B. V. All rights reserved.