Effects of Ga doping on the phase transitions of V2O3

Abstract

${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ undergoes a first-order metal-insulator transition accompanied by a magnetostructural transition at ${T}_{\mathrm{MI}}\ensuremath{\sim}160\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Here, we report a comprehensive study on gallium-doped (4%) polycrystalline ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ by employing various experimental techniques such as synchrotron x-ray diffraction, thermal expansion, Raman spectroscopy, DC magnetization, time-of-flight neutron diffraction, heat capacity, and electrical transport. Our studies show several interesting features related to the structural, magnetic, and electronic phase transitions in Ga-doped sample. Intriguingly, the nonmagnetic doping in ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ enhances the N\'eel temperature by 25 K $({T}_{\mathrm{N}}=185\phantom{\rule{0.16em}{0ex}}\mathrm{K})$. Further, we find the decoupling of the structural transition from the magnetic and insulator-insulator transition $({T}_{\mathrm{II}}\ensuremath{\sim}185\phantom{\rule{0.16em}{0ex}}\mathrm{K})$. Raman spectroscopic studies reveal that the structural phase transition begins at ${T}^{*} (=195\phantom{\rule{0.16em}{0ex}}\mathrm{K})$, which is slightly above ${T}_{\mathrm{N}}$ or ${T}_{\mathrm{II}}$, as evidenced from the softening of ${E}_{g}$ mode and the splitting of ${A}_{1g}$ mode. Additionally, the rhombohedral and monoclinic phases coexist in a broad temperature range, and a complete phase transformation to monoclinic phase occurs at 127 K.