The growth of magnetic clusters by annealing melt spun Co 10Cu 90 ribbons has been investigated with magnetic force microscopy (MFM) and conventional magnetometry. No clear magnetic structures were observed by MFM in the as-quenched samples. After annealing the samples at 500°C, magnetic Co particles with a mean size of 110±30 nm were observed. Further annealing to 750°C increased the Co particle size, which reaches a maximum value of 600 nm, and multidomain magnetic structures were observed. The magnetization reversal of these Co nanoparticles was observed by MFM with in situ applied magnetic fields. The MFM observations of an increase in both the density and size of stable Co nanoparticles with increased annealing temperatures are in qualitative agreement with the magnetometry data which indicate a doubling of the magnetization of the Co 10Cu 90 ribbons after annealing at 750°C.
Bibliographical noteFunding Information:
This work has been partially financed by the Spanish Comisión Interministerial de Ciencia y Tecnología (CICYT) in the Project No. MAT98-0404 and by the MRSEC Program of the National Science Foundation under Award Number No. DMR-0212302. One of the authors (J.V.) acknowledges the financial support from the Universidad Pública de Navarra, and also the professional and personal support from Professor V. Madurga, for his visit to the Magnetic Microscopy Center at the University of Minnesota.