Relation between Crystal and Magnetic Structures of Layered Manganite La_<2-2x>Sr_<1+2x>Mn_2O_7(0.30≤x≤0.50) : Condensed Matter: Electronic Properties etc.

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The magnetic phase diagram of La_<2-2x>Sr_<1+2xMn_2O_7 (0.30 ⪇ x ⪇ 0.50) was reexamined from the point of view of the crystal structure, particularly the Jahn-Teller (JT) distortion Δ_<JT> of Mn-O_6 octahedra, i.e., the ratio of the averaged apical Mn-O bond length to the equatorial Mn-O bond length. We have found that Δ_<JT> decreases with increasing hole concentration x, while the canting angle between neighboring planes continuously increases from 0°(planar ferromagnet: 0.32 ⪇ x ⪇ 0.38) to 180°(A-type antiferromagnet (AFM): x =0.48). The dominance of the A-type AFM structure with the decrease of Δ_<JT> can be ascribed to the change in the e_g orbital state from d_<3z^2-r^2> to d_<x^2-y^2>.
社団法人日本物理学会の論文
2000-06-15