DETERMINATION OF THE UPPER LIMIT OF THE MAGNETIC-MOMENT IN THE MAGNETORESISTANCE BY USING ITS IRREVERSIBLE TEMPERATURE AND SQUARE MAGNETIZATION DEPENDENCES IN (CU-RICH)-TM MELT-SPUN SYSTEMS

We have produced Cu-80(Fe0.5Ni0.5)(20) melt-spun granular ribbon sampl es whose magnetization is a superposition of superparamagnetic and hys teretical behavior at temperatures between 1.5 and 300 K. In contrast, its magneto-resistance (MR) data show hysteresis only at temperatures below 30 K. Above this temperature, a completely reversible behavior is observed. By considering the temperature dependence of the coercive field of nanoparticles, we determine the particles participating in M R to have a maximum magnetic moment of approximate to 27000 mu(B) for the 500 degrees C annealed sample. This value is in agreement with the limits obtained by fitting the data of MR as proportional to the squa re of the magnetization, assuming a distribution density of magnetic m oments proportional to the inverse of the square of the magnetic momen t of each cluster. (C) 1997 American Institute of Physics.