Studies on multifunctional behaviour of Cr doped SrWO₄ Compounds

Transition metal doped divalent tungstate compounds endowed with coalescence of optical and magnetic property forms a class of multifunctional materials and found importance in the field of magneto-optical and spintronics device applications. In the present work, pure and Cr doped SrWO₄ compounds were synthesized by chemical precipitation method. Powder X-ray diffraction analysis reveals scheelite type tetragonal structure of all the compounds. The effect of doping on crystal symmetry and local structure of the compounds was investigated by Laser Raman spectroscopy studies. The micro sphere and poly-dispersed surface morphology of all the compounds were examined by scanning electron microscopy and transmission electron microscopy analysis. Further, the evidences for oxygen vacancy and oxidation states of elements present in the compounds were analyzed by X-ray photoelectron spectroscopy. The optical absorption spectra explicitly describe the distinctive shift in absorption edge and linear decrease in band gap values while increasing Cr concentrations in SrWO₄ system. The presence of defective states and oxygen vacancy in Cr doped SrWO₄ compounds were confirmed with multicolor PL emission spectra. Electron paramagnetic resonance spectra authenticates the inducement of paramagnetic center (Cr³⁺) on increasing the dopant concentration. The magnetization analysis demonstrates enhanced ferromagnetic behaviour of all the Cr doped compounds, whereas the pure SrWO₄ compound exhibits frustrated ferromagnetic behaviour. The augmented ferromagnetic ordering in Cr doped compounds has been explained in terms of carrier-induced Ruderman–Kittel–Kasuya–Yosida interaction theory. The possible inducement of carrier mediated room temperature ferromagnetism in Cr doped SrWO₄ explicit demonstrates a hopeful candidature for magneto- optical and spintronic device applications.