X-RAY K-EDGE ABSORPTION AND MAGNETIC-BEHAVIOR OF CHROMIUM IN STOICHIOMETRIC AND NONSTOICHIOMETRIC ALPHA-CR2O3

The chemical shift in stoichiometric and nonstoichiometric alpha-Cr2O3 was determined from the X-ray absorption Cr K edge spectra. The diffe rence in the chemical shifts is produced by the decrease in the valenc e charge of chromium in the nonstoichiometric compound. Measurements o f the temperature dependence of the reciprocal susceptibility between 100 and 1200 K show an antiferromagnetic behaviour for both compounds, with the Neel temperature at 318 K. A big difference in the paramagne tic region was revealed for the compounds investigated. For both compo unds, between 318 and 530 K the magnetic susceptibility obeys the Curi e-Weiss law, with an effective magnetic moment per chromium ion of 4.8 6(mu B), very close to the calculated value of 4.9(mu B)/Cr2+. For the stoichiometric compound, over 530 K, the slope of the Curie-Weiss lin e increases and the effective magnetic moment is 3.83(mu B), very clos e to the calculated value of 3.8(mu B)/Cr3+.