Interplay of the CE-Type Charge Ordering and the A-Type Spin Ordering in Half-Doped Bilayer Manganite LaSr2Mn2O7

We demonstrate that the half-doped bilayer manganite La₁Sr₂Mn₂O₇ exhibits CE-type charge-ordered and spin-ordered states below TN, COA = 210 K and below TNCE ~ 145 K, respectively. However, the volume fraction of the CE-type ordering is relatively small, and the system is dominated by the A-type spin ordering. The coexistence of the two types of ordering is essential to understand its transport properties, and we argue that it can be viewed as an effective phase separation between the metallic d(x²-y²) orbital ordering and the charge-localized d(3x²-r²)/d(3y²-r²) orbital ordering.