Order–disorder phenomena in the charge–orbital sectors of half-doped manganites with the two-dimensional Mn–O network

We have investigated the magnetic, electrical, structural, as well as the orbital properties of high-quality single crystals of R 0.5 A 1.5 MnO 4 manganites with the two-dimensional (2D) Mn–O network. The long-ranged charge- and orbital-order established for crystals with small bandwidth and quenched disorder was found to be replaced by an homogeneous disordered “CE-glass” state as the bandwidth (related to the average ionic radius of the cations on the A -site, r A ) and the quenched disorder associated with the solid solution of the A -site cations (measured by the ionic radius variance σ 2 ) increase by substitution. Our results are compared to the three-dimensional (3D) perovskite case, which exhibits similar bandwidth-disorder phase diagram in low-bandwidth regions.