Enhanced stability of charge and orbital order in La0.78Sr2.22Mn2O7 -: art. no. 104403

Not only is zigzag charge and orbital (CO) order shown to be present in the highly doped (x=0.61) bilayered manganite system La2-2xSr1+2xMn2O7, it demonstrates an enhanced stability relative to the x=0.5 composition where the ordered state might be expected to have the lowest entropy. No magnetic-field dependence is observed up to 5.25 T. The CO ordering temperature also increases from 210 K at x=0.5 to 230 K, and the broad hysteretic conversion of the CO-ordered state to the A-type AF state at low temperatures is only partial. Phase reorganization in this hysteretic mixed-phase region is seen to involve an exponential time relaxation above T=50 K, while reorganization ceases below 50 K, apparently due to the thermally activated nature of the underlying dynamics.