Magnetic anisotropy in hole-doped superconducting Ba 0.67K 0.33Fe 2As2 probed by polarized inelastic neutron scattering

Abstract

We use polarized inelastic neutron scattering (INS) to study spin excitations of optimally hole-doped superconductor Ba${}_{0.67}$K${}_{0.33}$Fe${}_2$As${}_2$ ($T_c=38$ K). In the normal state, the imaginary part of the dynamic susceptibility, ${\chi }^{\prime \prime }(Q,\omega )$, shows magnetic anisotropy for energies below $\sim$7 meV with c-axis polarized spin excitations larger than that of the in-plane component. Upon entering into the superconducting state, previous unpolarized INS experiments have shown that spin gaps at $\sim$5 and 0.75 meV open at wave vectors $Q=(0.5,0.5,0)$ and $(0.5,0.5,1)$, respectively, with a broad neutron spin resonance at $E_r=15$ meV. Our neutron polarization analysis reveals that the large difference in spin gaps is purely due to different spin gaps in the c-axis and in-plane polarized spin excitations, resulting resonance with different energy widths for the c-axis and in-plane spin excitations. The observation of spin anisotropy in both opitmally electron and hole-doped BaFe${}_2$As${}_2$ is due to their proximity to the AF ordered BaFe${}_2$As${}_2$ where spin anisotropy exists below $T_N$.

arXiv comment5 pages, 4 figures

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• 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
• Unravelling incommensurate magnetism and its emergence in iron-based superconductors
• Electronic structure and spin dynamics of ACo2As2 (A=Ba, Sr, Ca)
• Spin-Orbit Coupling and Magnetic Anisotropy in Iron-Based Superconductors
• Spin anisotropy due to spin-orbit coupling in optimally hole-doped Ba${}_{0.67}$K${}_{0.33}$Fe${}_2$As${}_2$
• Double magnetic resonance and spin anisotropy in Fe-based superconductors due to static and fluctuating antiferromagnetic orders
• Suppression of spin-exciton state in hole overdoped iron-based superconductors
• Spin excitation anisotropy in optimal-isovalent-doped superconductor BaFe2(As0.7P0.3)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
• Suppression of low-energy longitudinal spin-excitations in Co-underdoped BaFe2As2
• Preferred magnetic excitations in Sr${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
• Strong Spin Resonance Mode associated with suppression of soft magnetic ordering in Hole-doped Ba1-xNaxFe2As2
• Spin excitation anisotropy in the paramagnetic tetragonal phase of BaFe2 As2
• Spin-Excitations Anisotropy in the Bilayer Iron-Based Superconductor CaKFe${}_4$As${}_4$
• Raman scattering study of tetragonal magnetic phase in Sr${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$: structural symmetry and electronic gap
• Unusual suppression of a spin resonance mode with magnetic field in underdoped NaFe${}_{1-x}$Co${}_x$As: Evidence for orbital-selective pairing
• Temperature and polarization dependence of low-energy magnetic fluctuations in nearly-optimal-doped NaFe${}_{0.9785}$Co${}_{0.0215}$As
• Neutron spin resonance as a probe of superconducting gap anisotropy in partially detwinned electron underdoped NaFe${}_{0.985}$Co${}_{0.015}$As