A Tunnel Magnetic Junction of high magnetoresistance is prepared at temperatures and pressure consistent with Si CMOS fabrication and operation. A first metal layer of cobalt or nickel is grown on an interconnect or conductive array line of e.g., copper. The metal layer is formed by electron beam irradiation. Annealing at UHV at temperatures below 700K yields a carbon segregation that forms a few layer thick (average density 3.5 ML) graphene film on the metal layer. Formation of a second layer of metal on top of the graphene barrier layer yields a high performance MTJ.