Properties of Nanocomposites With Different Concentrations of Magnetic Ions in an Insulating Matrix

Using (Co40Fe40B20)(x)(LiNbO3)(100-x) (x = 6-55 at.%) nanocomposite films as an example, we have performed comparative investigations of granular systems properties with a high (similar to 10(22) cm(-3)) and low (<= 10(21) cm(-3)) content of dispersed atoms (Fe and Co) in an insulating nonstoichiometric matrix. The nanocomposite films were produced using ion-beam sputtering of the composite targets onto glass-ceramic substrates at different growth temperatures (similar to 40 and similar to 80 degrees C). We show that magnetic ions dispersed in a matrix play a crucial role both in the ferromagnetic exchange between granules and in magnetic, transport, and memristive properties below the percolation threshold x(p) approximate to 50-55 at.%. The presence of a high content of dispersed magnetic ions induces intergranular interaction, shifts the critical concentration of the metal-insulator transition x(c) from 48 to 43 at.%, leads to high-field positive magnetoresistance near x(p) and superferromagnetic ordering and magnetic hysteresis below x(c) (down to 33 at.%), and makes the stable resistive switching for capacitorlike structures with resistance ratio R-OFF/R-ON more than 10(2) at x approximate to 10 at.%.