MOSSBAUER-SPECTROSCOPY OF CUO AND ITS RELEVANCE TO HIGH-TEMPERATURE SUPERCONDUCTORS

Mössbauer emission spectroscopy and magnetic susceptibility studies were performed on doped57 antiferromagnetic CuO. Magnetic susceptibility data show that antiferromagnetic ordering occurs at TN=225 K and that the Co dopant (10 100 ppm) does not influence the bulk magnetic properties of CuO. Mössbauer spectra recorded at T>244 K show a dominant quadrupole-split site and two minor impurity sites. At T=244 K, a line broadening of the dominant site is observed indicating the onset of local magnetic order. The hyperfine interaction parameters at T<TN were determined. In particular, the sign and the asymmetry parameter of the electric-field gradient (Vzz) and the angle formed by Vzz and magnetic hyperfine field were derived. We find to be very small (0.09) and 21° 28°. The value of is in accord with neutron-diffraction results. The Fe57 Mössbauer spectroscopy of CuO is discussed in relation to other copper oxides and Fe containing perovskites. © 1990 The American Physical Society.