Tunneling magneto-resistance granular thin films deposited by thermo-ionic vacuum arc technique

: Co-MgO granular films presenting TMR effects were prepared by thermo-ionic vacuum arc (TVA) method with the simultaneous ignition of plasma in Co and MgO vapors, respectively. The processing method is suitable for the simultaneous preparation of films of different relative content of Co in the MgO insulating matrix. Morphologic, structural and magnetic behaviors were analyzed in as prepared and annealed samples. The influence of the Co content on the magnetic properties of the prepared films was analyzed, in correlation with tunneling magneto-resistance effects. The tunneling magneto-resistance effect is maximal for certain Co content. This behavior was interpreted by the contrary effects of decreasing the average size of the magnetic grains, and hence the average inter-grains distance at higher Co relative content, and the enhanced magnetic disorder in very fine grains dispersed in the insulating matrix. This mechanism was suggested by the comportment of as prepared and thermally annealed samples.