Symmetry of reentrant tetragonal phase in Ba1-xNaxFe2As2: Magnetic versus orbital ordering mechanism

Article

关键词: NEMATIC ORDER;    IRON;    TRANSITIONS;   

DOI  :  10.1103/PhysRevB.90.174511

来源: SCIE

【 摘 要 】

Magnetostructural phase transitions in Ba(1-x)A(x)Fe(2)As(2) (A = K, Na) materials are discussed for both magnetically and orbitally driven mechanisms, using a symmetry analysis formulated within the Landau theory of phase transitions. Both mechanisms predict identical orthorhombic space-group symmetries for the nematic and magnetic phases observed over much of the phase diagram, but they predict different tetragonal space-group symmetries for the newly discovered reentrant tetragonal phase in Ba1-xNaxFe2As2 (x similar to 0.24-0.28). In a magnetic scenario, magnetic order with moments along the c axis, as found experimentally, does not allow any type of orbital order, but in an orbital scenario, we have determined two possible orbital patterns, specified by P4/mnc1' and I4221' space groups, which do not require atomic displacements relative to the parent I4/mmm1' symmetry and, in consequence, are indistinguishable in conventional diffraction experiments. We demonstrate that the three possible space groups are, however, distinct in resonant x-ray Bragg diffraction patterns created by Templeton & Templeton scattering. This provides an experimental method of distinguishing between magnetic and orbital models.

【 授权许可】

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