Room temperature tunneling magnetoresistance of electron beam deposited (Co50Fe50)x(Al2O3)1−x cermet granular films

Abstract

A series of (Co50Fe50)x-(Al2O3)1−x cermet granular thin films deposited on glass substrates by dual electron beam evaporation was studied for their structural, magnetotransport, and magnetic properties. Upon varying the magnetic volume fraction, x, from 0.07 to 0.52 the percolation threshold (xc) was determined from resistivity measurements to be ∼0.17. This value agrees well with the theoretical prediction for a three-dimensional system of spherical particles. Values of the isotropic tunneling magnetoresistance (TMR) as high as 10% at room temperature were found for films with x<0.16. The relationship between magnetotransport (maximum TMR) and the granular film topology (the percolation threshold) is discussed.