X-ray photoelectron spectroscopy (XPS) and magnetization studies of iron-sodium borate glasses

Iron-sodium borate glasses with the chemical composition [(B2O3)(0.70-x)(Na2O)(0.3)(Fe2O3)(x)], where 0.00 less than or equal to x less than or equal to 0.15, have been prepared and investigated by X-ray photoelectron spectroscopy (XPS) and magnetization measurements. The core-level binding energies of O Is, B Is, and Fe 2p have been measured with both O Is and B Is peaks shifting by about 2 eV towards smaller binding energies in the Fe-containing borate glasses while the Fe 2p(3/2) and 2p(1/2) core levels for the glasses remain essentially unchanged from those of Fe2O3 powder. The O Is spectrum is deconvoluted into two peaks and the variation in the ratio of the peak areas is discussed in terms of the local iron structure. We suggest that both X-ray photoelectron spectroscopy and magnetization measurements show that the Fe ions remain essentially in one oxidation state, probably Fe3+, for the Fe borate glasses. In addition, the appearance of a large hysteresis between the zero field-cooled and field-cooled magnetization data indicate that the Fe moments are clustered and that the predominant interaction is antiferromagnetic. (C) 1999 Elsevier Science B.V. All rights reserved.