Experimental evidence for anisotropic double exchange interaction driven anisotropic transport in manganite heterostructures

An anisotropic double exchange interaction driven giant transport anisotropy is demonstrated in a canonic double exchange system of La 2/3 Sr 1/3 MnO 3 ultrathin films epitaxially grown on NdGaO 3 (110) substrates. The oxygen octahedral coupling at the La 2/3 Sr 1/3 MnO 3 /NdGaO 3 interface induces a planar anisotropic Mn-O-Mn bond bending, which causes a significant anisotropic overlap of neighboring Mn orbitals. Due to the anisotropic double exchange interaction, it is found that the conductivity of the La 2/3 Sr 1/3 MnO 3 film is enhanced when current is applied along the in-plane short crystalline axis. However, the anisotropic behavior is absent in the high temperature paramagnetic phase. Our results demonstrate anisotropic transport in the clean limit where phase separation is absent and the role of anisotropic phase percolation can be excluded.