Spin reorientation to a Γ3(Cx, Fy, Az) configuration and anisotropic spin-phonon coupling in a Sm0.5Y0.5FeO3 single crystal

An unusual temperature-induced spin reorientation transition from ${\mathrm{\ensuremath{\Gamma}}}₂({F}_x, {C}_y, {G}_z)\ensuremath{-}{\mathrm{\ensuremath{\Gamma}}}₂₃\ensuremath{-}{\mathrm{\ensuremath{\Gamma}}}₃({C}_x, {F}_y, {A}_z)$ in orthoferrite ${\mathrm{Sm}}_0.5{\mathrm{Y}}_0.5{\mathrm{FeO}}₃$ is observed in the range 282--312 K through magnetic susceptibility measured on oriented single crystals. The ${\mathrm{\ensuremath{\Gamma}}}₂\ensuremath{-}{\mathrm{\ensuremath{\Gamma}}}₂₃\ensuremath{-}{\mathrm{\ensuremath{\Gamma}}}₃$ transition is distinctly different from the spin configurations commonly observed in $R{\mathrm{FeO}}₃$ orthoferrites, and we corroborate the finding with results from Raman spectroscopic investigations. Observation of magnon spectra and the vivid correlation between spin reorientation and changes in ${B}_2g$ and ${B}_3g$ phonon modes unveil strong spin-phonon coupling prevalent in ${\mathrm{Sm}}_0.5{\mathrm{Y}}_0.5{\mathrm{FeO}}₃$ crystal.