Optical excitations and ferromagnetic ordering in Sm doped WO3 at dilute concentrations

Sm doped WO3 (hereafter referred as WO3:Sm) compounds were synthesized via conventional solid-state reaction method and characterized for their structural, optical, and magnetic properties. X-ray diffraction (XRD) and the Rietveld refinement studies along with the Raman spectroscopy confirm that these compounds are of monoclinic phase [space group- P2(1)/n] with absence of impurities. Scanning Electron Microscopy (SEM) reveals that particles are densely packed with irregular morphologies. The UV-vis spectra show the band gap broadening with Sm doping due to the Burstein-Moss shift. The Photoluminescence studies (PL) under 320 nm excitation exhibit a broad-band of violet-blue emissions originating from oxygen vacancy defects of WO3. At 450 nm excitation, WO3:Sm samples show diffused Sm3+ emissions that could be due to the strong electron-phonon coupling between Sm ions and host lattice. The values of Commission Internationale de l'Elcairage (CIE) chromaticity coordinates and correlated color temperature (CCT) endorse cool white-light emission under 400 nm excitation making them a promising candidate for white LEDs. Magnetic measurements in these samples show the presence of room-temperature ferromagnetism (RTFM). The origin of the FM behavior is understood based on the bound magnetic polaron (BMP) mechanism and the magnetic data fit well with the BMP model.

Automated summary

The WO3:Sm compounds synthesized via solid-state reaction method were characterized for their structural, optical, and magnetic properties. The results showed monoclinic phase structure, densely packed particles, band gap broadening, violet-blue emissions, and room-temperature ferromagnetism, making them suitable for white LEDs.