Successive structural transitions coupled with magnetotransport properties inLaSr2Mn2O7

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 $x=0.5\mathrm{}$) which undergoes the charge-ordering below $\sim 210\hspace{0.5em}\mathrm{K}.$ The charge-ordered state associated with the $d_{{3x}^2-r^2}{/d}_{{3y}^2-r^2}$ 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.