Magnetic and transport properties of discontinuous metal-oxides multilayers

We report on structural, magnetic and transport properties of Al2O3/CoFe discontinuous multilayers deposited by RF sputtering at room temperature on silicon substrate. Transmission electron microscopy observations show that these multilayers consist of discontinuous layers of CoFe particles embedded in an insulating Al2O3 matrix. This is further supported by magnetization measurements showing the presence at room temperature of both superparamagnetic and ferromagnetic components. The current-in-plane resistivity of the discontinuous multilayers has shown a negative magnetoresistance due to a spin-dependent tunneling between the CoFe magnetic particles through the insulating Al2O3 barrier. The magnetoresistance response gives rise to two spin-dependent tunneling contributions. A contribution at small applied fields due to ferromagnetic particles and a contribution at larger magnetic applied fields due to a superparamagnetic particles.