Electronic phase diagram of half-doped perovskite manganites on the plane of quenched disorder versus one-electron bandwidth

For half-doped manganese oxides that have a perovskite structure, RE(1-x)AE(x)MnO(3) (x = 0.5) (RE and AE are rare-earth and alkaline-earth elements, respectively), the phase competition (stability) between the antiferromagnetic charge-or orbital-ordered insulator (CO/OO AFI), ferromagnetic metal (FM), layered (A-type) antiferromagnetic phase [AF(A)], and spin-glass-like insulator (SGI), have been studied using single crystals prepared by the floating zone method. The CO/OO AFI, FM, AF(A), and SGI are displayed on the plane of the disorder (the variance of the RE and AE cations) versus the effective one-electron bandwidth (the averaged ionic radius of the RE and AE). In the plane of the disorder versus the effective one-electron bandwidth, similar to the phase diagram of RE(1-x)AE(x)MnO(3) (x = 0.45), the CO/OO AFI, FM, and SGI dominate at the lower-left, right, and upper regions, respectively. However, the CO/OO AFI for x = 0.5 is more stable than that for x = 0.45, and it expands to the plane points that correspond to the RE0.5Sr0.5MnO3 (RE = Nd and Sm) specimens as the hole concentration is commensurate with the ordering of Mn3+/Mn4+ with a ratio of 1/1. The y-dependent electronic phases for RE0.5(Sr1-yBay)(0.5)MnO3 (0 <= y <= 0.5) (RE = Sm, Nd0.5Sm0.5, Nd, and Pr) show that the AF(A) intervenes between the CO/OO AFI and FM. Besides the region around (La1-yPry)(0.5)Sr0.5MnO3 (0 <= y <= 1) that has a smaller disorder, the AF(A) also exists at the regions around RE0.5(Sr1-yBay)(0.5)MnO3 (0 < y < 0.3) (RE = Sm and Nd0.5Sm0.5) that have a relatively larger disorder. This indicates that the AF(A) is rather robust against the increased disorder, even though an ordering of the (x(2) - y(2)) orbital occurs. This study has comprehensively investigated the effects of the disorder on the AF(A) as well as on the competition between the CO/OO AFI, FM, and AF(A) that is unique to x = 0.5. The comparison of phase diagrams between x = 0.45 and 0.5 brings further insights into the understanding of the rich electronic phases of manganites.