MAGNETORESISTANCE AND LOCAL MAGNETIC ORDER IN RANDOM ANISOTROPY FERROMAGNETIC SYSTEMS

In ferromagnetic systems with random anisotropy (RA), long range magne tic order is destroyed and the correlation function of the magnetizati on presents an exponential form e(-r/R)f. Also, the law of approach to saturation follows a 1/square-root H law (Ferromagnet with Wandering Axis regime). We calculated the effect of magnetic correlations on the resistivity of a RA ferromagnetic system at low temperatures. In the FWA regime the magnetoresistance has a logarithmic dependence on the m agnetic field and the slope of that variation is inversely proportiona l to the correlation length, R(f). This is verified by magnetoresistan ce measurements in amorphous alloys with RA (with Dy). The logarithmic dependence was observed in extended field ranges (1-50 kOe), and the values obtained for R(f) are in agreement with the ones determined fro m magnetic measurements.