Influence of particle size distribution in cermet nanocomposites on magnetoresistance sensitivity

Tunneling magnetoresistance (TMR) and magnetic properties of (Co/sub 50/Fe/sub 50/)/sub x/-(Al/sub 2/O/sub 3/)/sub 1-x/ granular films prepared by dual electron beam evaporation were studied. The influence of the particle size distribution (PSD) on magneto-transport properties is reported. It was found that TMR versus M behavior does not follow (M/M/sub s/)/sup 2/ law (M and M/sub s/ are magnetization and saturation magnetization, respectively), predicted for uniform size spherical particles with uncorrelated magnetic moments. Deviation from quadratic law is determined by PSD and is maximal for the films with the broadest distribution of superparamagnetic particles. For these films, the highest values of TMR and field sensitivity were also observed. The effect of PSD could be used for enhancement of TMR sensitivity in granular nanocomposites.