Abstract
Neutron powder diffraction measurements were carried out in A-site ordered perovskite manganese oxides TbBaMn2O6 and NdBaMn2O6. Analysis of magnetic reflections in TbBaMn2O6 shows that the magnetic structure is characterized by two kinds of magnetic modulation vectors, (1/2 0 1/4) and (1/4 1/4 1/4), in the primitive cubic setting. The most possible arrangement of spin, charge, and orbital degrees of freedom was proposed. In NdBaMn2O6, the so-called A-type antiferromagnetic structure was observed below-280K. Change of the lattice constants below TN strongly indicates that the A-type AFM was accompanied by x2-y2-type orbital ordering.
