Phase Stability and Magnetic Behaviour in Fe-doped Cupric Oxide Powders

SILVANA JACQUELINE STEWART; R. A. BORZI; G. PUNTE; R. C. MERCADER

Physical Review B - Condensed Matter and Materials Physics

Año: 1998 vol. 57 p. 4983 - 4986

0163-1829

We performed ball milling ~BM! to powders of CuO and 0.25 mol. % of a- 57Fe2O3, and next annealed thesamples in air in cumulative 40-h steps up to 1000 K. We analyzed the samples by x-ray diffraction ~XRD! andMo¨ssbauer spectroscopy. Up to the annealing at 800 K a significant part of the 57Fe forms a Cu~Fe!O solidsolution. The magnetic behavior of the CuO particles is reflected in the Mo¨ssbauer spectra that display anaverage value of 28 T of a broad magnetic hyperfine field distribution at 15 K. The XRD results show that theCuO particles have an average size of '7 nm and a significant degree of strain after BM. Their sizes increasewith the successive thermal treatments, and the strain is gradually released. Small particles of CuFe2O4 spinelare found to form after the 850-K annealing.