Magnetoresistance of Mn : Ge ferromagnetic nanoclusters in a diluted magnetic semiconductor matrix

We have fabricated a thin film magnetic system consisting of nanoscale Mn11 Ge8 ferromagnetic clusters embedded in a MnxGe1-x dilute ferromagnetic semi conductor matrix. The clusters form for growth temperatures of similar to 3 00 degreesC with an average diameter and spacing of 100 and 150 nm, respect ively. While the clusters dominate the magnetic properties, the matrix play s a subtle but interesting role in determining the transport properties. Va riable range hopping at low temperatures involves both nanoclusters and Mn- Ge sites, and is accompanied by a negative magnetoresistance attributed in part to spin-dependent scattering analogous to metallic granular systems. ( C) 2001 American Institute of Physics.