Successive structural transitions coupled with magnetotransport properties inLaSr2Mn2O7

Abstract

Temperature variations of the lattice structure and the magnetotransport properties have been investigated for a bilayered manganite crystal ${\mathrm{LaSr}}_{2}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ (hole-doping level of $x=0.5$) which undergoes the charge-ordering below $\ensuremath{\sim}210 \mathrm{K}.$ The charge-ordered state associated with the ${d}_{{3x}^{2}\ensuremath{-}{r}^{2}}{/d}_{{3y}^{2}\ensuremath{-}{r}^{2}}$ orbital ordering of ${\mathrm{Mn}}^{3+}$ appears to collapse again with decreasing temperature below 50--100 K, which was proved by both measurements of electron and x-ray diffraction. The structural change or the switching of the orbital state in this bilayered manganite manifests itself in temperature profiles of the charge-transport and magnetic properties.