Temperature and polarization dependence of low-energy magnetic fluctuations in nearly-optimal-doped NaFe${}_{0.9785}$Co${}_{0.0215}$As

Abstract

We use unpolarized and polarized neutron scattering to study the temperature and polarization dependence of low-energy magnetic fluctuations in nearly-optimal-doped NaFe${}_{0.9785}$Co${}_{0.0215}$As, with coexisting superconductivity ($T_{\mathrm{c}}\approx 19$ K) and weak antiferromagnetic order ($T_{\mathrm{N}}\approx 30$ K, ordered moment $\approx 0.02$ ${\mu }_{\mathrm{B}}$/Fe). A single spin resonance mode with intensity tracking the superconducting order parameter is observed, although energy of the mode only softens slightly on approaching $T_{\mathrm{c}}$. Polarized neutron scattering reveals that the single resonance is mostly isotropic in spin space, similar to overdoped NaFe${}_{0.935}$Co${}_{0.045}$As but different from optimal electron-, hole-, and isovalent-doped BaFe${}_2$As${}_2$ compounds, all featuring an additional prominent anisotropic component. Spin anisotropy in NaFe${}_{0.9785}$Co${}_{0.0215}$As is instead present at energies below the resonance, which becomes partially gapped below $T_{\mathrm{c}}$, similar to the situation in optimal-doped YBa${}_2$Cu${}_3$O${}_{6.9}$. Our results indicate that anisotropic spin fluctuations in NaFe${}_{1-x}$Co${}_x$As appear in the form of a resonance in the underdoped regime, become partially gapped below $T_{\mathrm{c}}$ near optimal doping and disappear in overdoped compounds.

to be published in PRB

References in corpus (16)

• Spin resonance in the d-wave superconductor CeCoIn5
• Itinerant magnetic excitations in antiferromagnetic CaFe2As2
• Nature of magnetic excitations in superconducting BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$
• Symmetry of spin excitation spectra in the tetragonal paramagnetic and superconducting phases of 122-ferropnictides
• Resonance in the electron-doped high-Tc superconductor Pr0.88LaCe0.12CuO(4-delta)
• Crossover from weak to strong pairing in unconventional superconductors
• Itinerant Spin Excitations in SrFe2As2 Measured by Inelastic Neutron Scattering
• Robust Upward Dispersion of the Neutron Spin Resonance in the Heavy Fermion Superconductor Ce${}_{1-x}$Yb${}_x$CoIn${}_5$
• Magnetic anisotropy in hole-doped superconducting Ba 0.67K 0.33Fe 2As2 probed by polarized inelastic neutron scattering
• Anisotropic neutron spin resonance in underdoped superconducting NaFe1-xCoxAs
• Polarized neutron scattering studies of magnetic excitations in electron-overdoped superconducting BaFe${}_{1.85}$Ni${}_{0.15}$As${}_2$
• Anisotropy of incommensurate magnetic excitations in slightly overdoped Ba${}_{0.5}$K${}_{0.5}$Fe${}_2$As${}_2$ probed by polarized inelastic neutron scattering experiments
• Magnonlike dispersion of spin resonance in Ni-doped BaFe${}_2$As${}_2$
• Spin anisotropy due to spin-orbit coupling in optimally hole-doped Ba${}_{0.67}$K${}_{0.33}$Fe${}_2$As${}_2$
• Crossover from spin-waves to diffusive spin excitations in underdoped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Spin excitation anisotropy in the paramagnetic tetragonal phase of BaFe2 As2

Cited by in corpus (2)

• Preferred Spin Excitations in the Bilayer Iron-Based Superconductor CaK(Fe${}_{0.96}$Ni${}_{0.04}$)${}_4$As${}_4$ with Spin-Vortex Crystal Order
• Nematic fluctuations in the non-superconducting iron pnictide BaFe${}_{1.9-x}$Ni${}_{0.1}$Cr${}_x$As${}_2$