⁵⁷Co emission studies of cupric oxide

Abstract

Results on the incorporation, valence and spin states of Fe(Co) in CuO (with reference to similar studies on high temperature superconductors) and coupling of the Fe(Co) moment to the Cu magnetism in CuO are presented. Freshly prepared⁵⁷Co: CuO shows two quadrupole doublets D₁ and D₂ withQ.S. of 2.49 and 1.52,I.S. of 0.35 and 0.70 mm/s and relative abundance of 74% and 26%, respectively at room temperature, the abundance being dependent on time in a sample exposed to ambient conditions and reaching 38 to 62% fifteen months after preparation. Below,T _N=225¹K, a typical combined magnetic-quadrupole interaction pattern is observed with a single saturation magnetic hfs of 25.6 T, central shift of 0.82 mm/s and a single |E _Q|=1.62 mm/s at 4.2 K. External magnetic field spectra reveal an antiferromagnetic behaviour of the Fe(Co) ion. Temperature dependence of the magnetic hfs is fitted in the framework of the molecular field approximation allowing different spins and coupling constants for Cu and Fe(Co).