Zener Polaron Ordering Variants Induced by A-Site Ordering in Half-Doped Manganites

摘要

We have studied the magnetism of the half-doped charge ordered manganite YBaMn_2O_6. A formation of ferromagnetic plaquettes of four Mn atoms in the charge ordered phase below T_(CO) ～ 480 K is inferred from high temperature magnetic susceptibility data and the magnetic structure, as determined by neutron powder diffraction at T = 1.5 K. The results indicate that new fourfold Mn paramagnetic units form between T_N < T < T_(CO) and that they order in a noncollinear mode below T_N = 190 K. The magnetism of YBaMn_2O_6 is consistent with what is expected from the Zener polarons ordering picture of the charge ordering phenomenon in manganites [A. Daoud-Aladine et al., Phys. Rev. Lett. 89, 097205 (2002)].