Structural origin of the pseudo-two-dimensional metallic state in the A-type antiferromagnetic manganites -: art. no. 132414

The interplay between the structure and A-type spin ordering in La0.46Sr0.54Mn0.98Cr0.02O3 (LSMO) has been studied using neutron powder diffraction. The antiferromagnetic transition is accompanied by a structural transition from tetragonal I4/mcm with lattice constant a=c<<b/root2 to monoclinic P2(1)/n with b/root2<<aapproximate toc (betaapproximate to90.4degrees). Moreover, the first-order A-type spin ordering is characterized by a two-dimensional-like (2D-like) anisotropic structural distortion [Delta(a,c)approximate to+1.05%, Deltab/root2approximate to-2.2%] and the unusual volume discontinuity (DeltaVapproximate to0.13%). These results demonstrate that the pseudo-2D metallic state in LSMO can be realized by a 2D-like anisotropic lattice distortion correlated with the A-type spin ordering and the d(x2-y2) orbital ordering.