PHASE-STABILITY AND MAGNETIC-BEHAVIOR OF FE-DOPED CUO POWDERS

We performed ball milling (BM) to powders of CuO and 0.25 mel. % of al pha-(Fe2O3)-Fe-57, and next annealed the samples in air in cumulative 40-h steps up to 1000 K. We analyzed the samples by x-ray diffraction (XRD) and Mossbauer spectroscopy. Up to the annealing at 800 K a signi ficant part of the Fe-57 forms a Cu(Fe)O solid solution. The magnetic behavior of the CuO particles is reflected in the Mossbauer spectra th at display an average value of 28 T of a broad magnetic hyperfine fiel d distribution at 15 K. The XRD results show that the CuO particles ha ve an average size of approximate to 7 nm and a significant degree of strain after BM. Their sizes increase with the successive thermal trea tments, and the strain is gradually released. Small particles of CuFe2 O4 spinel are found to form after the 850-K annealing.