Neutron powder diffraction investigation of the structural and magnetic properties of (La1-yYy)FeAsO

Abstract

The structural, magnetic and resistive properties of (La1-yYy)FeAsO compounds (y = 0.10, 0.20, 0.30) have been investigated by means of X-ray and neutron powder diffraction as well as by resistivity measurements. The temperatures at which the structural transition from tetragonal to orthorhombic and the magnetic ordering take place progressively reduce by similar amounts with increasing Y substitution on account of the progressive chemical pressure increase. We propose that the structural transition could be originated by a cooperative Jahn-Teller distortion involving the alignment of the fully occupied Fe 3d(z2) orbitals in the Fe plane along the y axis, leading to the branching of the cell parameters a and b. The magnetic structure develops after the occurrence of the structural transition, but before its completion.

27 pages, 9 figures

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• From antiferromagnetism to superconductivity in Fe 1+y(Te1-x,Sex) (0 < x < 0.20): a neutron powder diffraction analysis
• Effect of Ru susbstitution on atomic displacements in the layered SmFe_{1-x}Ru_xAsO_{0.85}F_{0.15} superconductor
• Microstructural evolution throughout the structural transition in 1111 oxy-pnictides
• Lattice anomalies in the FeAs${}_4$ tetrahedra of the NdFeAsO${}_{0.85}$ superconductor that disappear at T${}_{\mathrm{c}}$
• Emergence of superconductivity in single-crystalline LaFeAsO under simultaneous Sm and P substitution
• Phase separation at the magnetic-superconducting transition in La${}_{0.7}$Y${}_{0.3}$FeAsO${}_{1-x}$F${}_x$