Measuring Magnetoresistance in a 2D Intergranular Magnetic-Semiconducting Material

A new 2D intergranular semiconducting-magnetic material obtained by depositing magnetic clusters of permalloy in a doped Si surface, is presented. The material, exhibiting ohmic contacts, has an ample range of properties and versatility by simply controlling deposition time. We can have clusters separated by relatively large, intermediate distances or a continuous film. This permits to study the magnetic and electrical properties of the clusters mediated by currents through the n-doped Si. We observe anisotropic and giant magnetoresistances of and between clusters. Also, by preventing oxidation of the Si surface, we suggest the possibility of formation of magnetic Si up to 205 K. The material reported here is technologically promising since it is grown directly on Si and its magnetoresistance of up to 1.5% is obtained at low fields and RT. The spin transfer occurs for long distances since the current flows coherently from cluster to cluster via the Si matrix. The method developed may be also adequate to study superconductivity properties of isolated or weakly percolative clusters by coupling through Josephson currents. The system is diluted when clusters are separated on average by 50 nm. This could help to better understand dilute magnetic semiconductor materials in general. We also put forward a method to distinguish univocally giant from anisotropic magnetoresistance by depositing a thin film of gold and comparing magnetic properties by spin transfer through Si or metal.