10. "Shifting the Superparamagnetic Limit of Nanosized Copper Iron Spinel"

S. J. STEWART; ROBERTO CARLOS MERCADER; G. PUNTE; DESIMONI, J; G. CERNICCHIARO; R. B. SCORZELLI

Hyperfine Interactions

Año: 2004 vol. 156 p. 89 - 95

0304-3843

Using a co-precipitation method, a system formed by nanocrystalline copper ferrite, grain size (D)»6 nm, and CuO (15 wt.%) was obtained. A Mössbauer blocking temperature (TB) that lies between 100 and 200 K was observed. After milling for 10 h, TB increases to temperatures higher than 298 K. The DC and AC magnetic results also show the increment of TB. Simultaneously, the increase in the mean grain sizes (up to D »13 nm) and the decrease of the microstrain level indicate that the degree of crystallinity increases. The mean magnetic moment per grain raises and the amount of CuO decreases with the milling. The XRD pattern of the 10 h milled sample shows lines belonging only to nanocrystalline CuFe2O4 in its metastable cubic phase.