Exploration of the Electronic Structure of Monoclinic α-Eu2(MoO4)3: DFT-Based Study and X-ray Photoelectron Spectroscopy

The powder alpha-Eu-2(MoO4)(3) sample was prepared by the solid-state reaction method. The phase purity of the final powder product was verified by X-ray diffraction analysis. The constituent element core levels and valence band are measured by X-ray photoelectron spectroscopy as a function of Ar+ ion (2.5 keV, 7-8 mu A/cm(2)) bombardment time. The formation of Mo5+ and Mo4+ states at high bombardment times was detected. The Eu-O and Mo-O bonding was considered in comparison with other Eu3+- and Mo6+-containing oxides using binding energy difference parameters. The transparency range obtained for the pure alpha-Eu-2(MoO4)(3) tablet is lambda = 0.41-0.97 mu m, as estimated at the transmission level of 5%. The short-wavelength cut edge in alpha-Eu-2(MoO4)(3) is governed by the direct allowed optical transitions within the band gap of E-g = 3.74 eV (300 K). The band structure of alpha-Eu-2(MoO4)(3) was calculated by ab initio methods and strongly different results were obtained for the spin up/down configurations. The Eu-4f states are located around 2.2 eV and 4.0 eV for spin up (up arrow) and the structures situated at around 6.5 and 5.5 eV for spin down (down arrow) configuration. The calculated spin magnetic moments are in excellent relation to the Slater-Pauling rule and within the Eu sphere the magnetic moment of 4f electrons is, similar to 5.99 mu B.