Magnetic behavior of twin roller melt spun Cu90Co10 alloys

H. NÚÑEZ COAVAS; G. POZO LÓPEZ; L.M. FABIETTI; A.M. CONDÓ; S.E. URRETA

IEEE TRANSACTIONS ON MAGNETICS

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Lugar: New York; Año: 2013 vol. 49 p. 4518 - 4521

0018-9464

Magnetoresistive Cu90Co10 alloys are synthesized by twin roller melt spinning at tangential wheel speeds between 10 m/s and 30 m/s to obtain different solute and Co-rich precipitate distributions. X-ray diffraction indicates that the ribbons are polycrystalline with a fcc Cu(Co) (200) textured matrix; no evidence of a spinodal-like composition modulation could be detected with this technique. Transmission electron microscopy observations performed in samples quenched at 10 m/s indicate the existence of small, coherent, Co-rich precipitates of mean size of about 11 nm and bigger (~40 nm) Co-oxide particles. The small coherent precipitates form colonies inside the grains, mediated by precipitate free zones. Samples quenched at 30 m/s are single magnetic phase (superparamagnetic), but the hysteresis loops of the other as cast ribbons are well fitted by a superparamagnetic contribution and a ferromagnetic one, arising from the Co-rich precipitates. The room temperature coercivities, of about 30-50 mT, are lower than those predicted for a mechanism of coherent rotation in the ensemble of non-interacting, Co-rich precipitates.