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≤x≤0.15, have been prepared and investigated by X-ray photoelectron spectroscopy (XPS) and magnetization measurements. The core-level binding energies of O 1s, B 1s, and Fe 2p have been measured with both O 1s and B 1s 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 1s 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.