RESISTANCE FLUCTUATIONS IN AMORPHOUS CR74FE26 FILMS

Magnetoresistance measurements Delta rho/rho have been carried out on an amorphous Cr74Fe26 film in the temperature range of 4-120 K in a ma gnetic field up to 120 kOe. We observed that the isotropic component o f the magnetoresitance at low temperatures first decreases with increa sing field due to the decrease in the spin fluctuations (negative mag magnetoresistance), goes through a minimum at a certain field value, H -c and then starts to increase (positive magnetoresistance) as the mag netic field is further increased. As the temperature increases. H-c, s hifts ro a higher field and the magnetoresistance on both sides of thi s field (negative and positive magnetoresistance) decreases. The magne toresistance becomes almost zero at temperatures between 10-16 K. Howe ver, as the temperature is further increased, the magnetoresistance st arts to increase again. This overall behaviour with the resistivity da ta have been interpreted successfully in terms of localization effects . We have also observed huge oscillations in the resistivity at low fr equencies (7-70 mHz) in the temperature range where Delta rho/rho beco mes weaker. Starting with the temperature at about T = 15 K, the ampli tudes of these oscillations reduce with both increasing and decreasing temperatures. However, the frequencies of these oscillations increase with decreasing temperature. No detectable oscillation in the resisti vity has been observed at temperatures below T = 8 K and above T > T-c (the Curie temperature, T-c = 43.8 K). We have no full explanation fo r this phenomenon, however, it is tempting to ascribe it to some kind of spin density wave. (C) 1998 Elsevier Science B.V. All rights reserv ed.