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

Abstract

Magneto-structural phase transitions in Ba1-xAxFe2As2 (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 re-entrant tetragonal phase in Ba1-xNaxFe2As2 (x ~ 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.

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Cited by in corpus (20)

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• Charge Nematicity and Electronic Raman Scattering in Iron-based Superconductors
• Electronic nematic susceptibility of iron-based superconductors
• Hedgehog spin-vortex crystal stabilized in a hole-doped iron-based superconductor
• Magnetic interactions in iron superconductors: A review
• The phase diagrams of iron-based superconductors: theory and experiments
• Tetragonal magnetic phase in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ from x-ray and neutron diffraction
• Spin reorientation driven by the interplay between spin-orbit coupling and Hund's rule coupling in iron pnictides
• Detailed magnetic and structural analysis mapping a robust magnetic C4 dome in Sr1-xNaxFe2As2
• Muon-spin-rotation study of the magnetic structure in the tetragonal antiferromagnetic state of weakly underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Infrared study of the spin reorientation transition and its reversal in the superconducting state in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Superconductivity and electronic fluctuations in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ studied by Raman scattering
• Emergent magnetic degeneracy in iron pnictides due to the interplay between spin-orbit coupling and quantum fluctuations
• Intertwined spin-orbital coupled orders in the iron-based superconductors
• Magnetic phase diagram of the iron pnictides in the presence of spin-orbit coupling: Frustration between $C_2$ and $C_4$ magnetic phases
• Competing spin density wave, collinear, and helical magnetism in Fe1+xTe
• Muon spin rotation and infrared spectroscopy study of $B{a}_{1-x}N{a}_{x}F{e}_{2}A{s}_2$
• Mn(Pt${}_{1-x}$Pd${}_x$)${}_5$P: Isovalent Tuning of Mn Sublattice Magnetic Order
• Electronic and magnetic properties of orthorhombic iron selenide (FeSe)