Possible orbital ordering independent of charge or magnetic order in the A-site ordered manganite RBaMn2O6 with structural frustration

Abstract

We have grown single crystals of TbBaMn2O6 by a floating-zone method and studied the structural and electromagnetic properties, particularly focusing on the anisotropy of electromagnetic properties. TbBaMn2O6 shows successive transitions; the structural transition at 450 K. the metal-insulator transition accompanied by the charge/orbital order at 430 K and the antiferromagnetic transition at 220 K. The obtained results support the dx2-y2 orbital ordering at 450 K which is independent of the charge and magnetic order. This means the separation of orbital, charge and spin degrees of freedom in the A-site ordered manganite ABaMn2O6 (R = Tb, Dy, Ho and Y), which might originate in the inherent structural frustration.