Magnetic and magnetoresistance measurements on iron-based nanoclusters in In0.53Ga0.47As

We have obtained magnetoresistance data on low iron-concentration samples (∼1%) showing a large negative magnetoresistance (3.2% at 5 K in 0.5 T) attributed to imbedded superparamagnetic clusters in In0.53Ga0.47As. The samples were prepared by ion implanting a p-In0.53Ga0.47As layer with iron followed by a rapid thermal anneal. Magnetic measurements confirm the formation of a cluster size distribution with a mean diameter of 6.2 nm and effective moment of 7000 bohr magnetons. The magnetization of these single domain ferromagnets is 50% saturated in a field of only 0.2 T even at room temperature which is important for device applications.