Evidence for negative thermal expansion in the superconducting precursor phase SmFeAsO

Abstract

The fluorine-doped rare-earth iron oxypnictide series SmFeAsO${}_{1-x}$F${}_x$ (0 $\le x\le$ 0.10) was investigated with high resolution powder x-ray scattering. In agreement with previous studies, the parent compound SmFeAsO exhibits a tetragonal-to-orthorhombic structural distortion at T${}_{\mathrm{S}}$~=~130~K which is rapidly suppressed by $x\simeq$ 0.10 deep within the superconducting dome. The change in unit cell symmetry is followed by a previously unreported magnetoelastic distortion at 120~K. The temperature dependence of the thermal expansion coefficient ${\alpha }_V$ reveals a rich phase diagram for SmFeAsO: (i) a global minimum at 125 K corresponds to the opening of a spin-density wave instability as measured by pump-probe femtosecond spectroscopy whilst (ii) a global maximum at 110 K corresponds to magnetic ordering of the Sm and Fe sublattices as measured by magnetic x-ray scattering. At much lower temperatures than T${}_{\mathrm{N}}$, SmFeAsO exhibits a significant negative thermal expansion on the order of -40~ppm~$\cdot$~K${}^{-1}$ in contrast to the behavior of other rare-earth oxypnictides such as PrFeAsO and the actinide oxypnictide NpFeAsO where the onset of $\alpha <$ 0 only appears in the vicinity of magnetic ordering. Correlating this feature with the temperature and doping dependence of the resistivity and the unit cell parameters, we interpret the negative thermal expansion as being indicative of the possible condensation of itinerant electrons accompanying the opening of a SDW gap, consistent with transport measurements.

arXiv comment7 pages, 5 figures

References in corpus (47)

• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems
• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• Superconductivity in Iron Compounds
• Structural and magnetic phase diagram of CeFeAsO1-xFx and its relationship to high-temperature superconductivity
• Strong Correlations and Magnetic Frustration in the High Tc Iron Pnictides
• Competing Orders and Spin-Density-Wave Instability in La(O${}_{1-x}$F${}_x$)FeAs
• Theory of Electron Nematic Order in LaOFeAs
• Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO
• Ising and Spin orders in Iron-based Superconductors
• Phase transitions in LaFeAsO: structural, magnetic, elastic, and transport properties, heat capacity and Mossbauer spectra
• Electron-Hole Symmetry and Magnetic Coupling in Antiferromagnetic LaOFeAs
• Commensurate Spin Density Wave in LaOFeAs: A Local Probe Study
• Crystallographic Phase Transition and High-Tc Superconductivity in LaFeAsO:F
• Local Magnetic Order vs. Superconductivity in a Layered Cuprate
• Magnetic neutron scattering in hole doped cuprate superconductors
• From incommensurate to dispersive spin-fluctuations: The high-energy inelastic spectrum in superconducting YBa2Cu3O6.5
• Superconducting properties of Fe-based layered superconductor LaO${}_{0.9}$F${}_{0.1-\delta }$FeAs
• Dynamic Stripes and Resonance in the Superconducting and Normal Phases of YBa2Cu3O6.5 Ortho-II Superconductor
• Muon spin relaxation studies of incommensurate magnetism and superconductivity in stage-4 La${}_2$CuO${}_{4.11}$ and La${}_{1.88}$Sr${}_{0.12}$CuO${}_4$
• New Perspective on the Phase Diagram of Cuprate High-Temperature Superconductors
• Magnetic Order of the Iron Spins in NdOFeAs
• Magnetic-crystallographic phase diagram of superconducting parent compound Fe${}_{1+x}$Te
• Crystal structure and phase transitions across the metal-superconductor boundary in the SmFeAsO1-xFx (0 < x < 0.20) family
• Magnetic Ordering and Negative Thermal Expansion in PrFeAsO
• Competition of magnetism and superconductivity in underdoped (Ba1-xKx)Fe2As2
• Specific heat of the iron-based high-$T_c$ superconductor SmO${}_{1-x}$F${}_x$FeAs
• Non-collinear spin-density wave antiferromagnetism in FeAs
• MuSR studies of RE(O,F)FeAs (RE = La, Nd, Ce) and LaOFeP systems: possible incommensurate/stripe magnetism and superfluid density
• Interstitial iron tuning of the spin fluctuations in Fe1+xTe
• Quasiparticle relaxation dynamics in spin-density-wave and superconducting SmFeAsO_{1-x}F_{x} single crystals
• Central mode and spin confinement near the boundary of the superconducting phase in YBa2Cu3O6.353 (Tc=18 K)
• The magnetic and structural properties near the Lifshitz point in Fe1+xTe
• Pressure decoupled magnetic and structural transitions of the parent compound of iron based 122 superconductors BaFe2As2
• Weak spin interactions in Mott insulating La2O2Fe2OSe2
• Spin dynamics near the critical doping in weakly-superconducting underdoped YBa2Cu3O6.35 (Tc=18K)
• Transition Temperature and Upper Critical Field in SmFeAsO1-xFx Synthesized at Low Heating Temperatures
• Neutron scattering search for static magnetism in oxygen ordered YBa2Cu3O6.5
• Negative thermal expansion and antiferromagnetism in the actinide oxypnictide NpFeAsO
• Strong coupling of Sm and Fe magnetism in SmFeAsO as revealed by magnetic x-ray scattering
• Transport and infrared properties of SmFeAs(O1-xFx): from SDW to superconducting ordering
• Tetragonal to orthorhombic phase transition in SmFeAsO: a synchrotron powder diffraction investigation
• Soft striped magnetic fluctuations competing with superconductivity in Fe_{1+x}Te
• In Search of Microscopic Evidence for Molecular Level Negative Thermal Expansion in Fullerenes
• Spin fluctuations and superconductivity in powders of Fe_1+xTe_0.7Se_0.3 as a function of interstitial iron concentration
• Thermal expansion of RFeAsO (R=La,Ce,Pr,Sm,Gd)
• Magneto-transport and magnetic susceptibility of SmFeAsO1-xFx (x = 0.0 and 0.20)

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