Magnetic and structural properties of Cu–Co granular alloys measured with NMR

Abstract

59Co NMR experiments were performed in melt-spun Cu 100− x Co x samples ( x=10, 15 and 20). The NMR spectra are very similar for all concentrations. A seven-line structure equally spaced by 18 MHz was observed, with frequencies lower than that of metallic cobalt (217 MHz). This result is interpreted as a step decrease of the Co resonance frequency with each additional Cu impurity in the first coordination shell. The presence of the satellite lines indicates that the grains are very small, and the interface contributions prevail over those of the bulk. Regions with two different local anisotropy field values were observed for x=15 (∼0.1 and ∼1 kG). For x=10 and 20, a single anisotropy value was found.