Low energy spin dynamics in the antiferromagnetic phase of CaFe2As2

Abstract

We present 75As nuclear magnetic resonance data in the paramagnetic and magnetic states of single crystal CaFe2As2. The electric field gradient and the internal magnetic field at the As sites change discontinuously below the first order structural transition at T0 = 169 K. In the magnetic state, we find a single value of the internal hyperfine field consistent with commensurate antiferromagnetic order of Fe moments pointing in the ab plane. The spin lattice relaxation rate shows Korringa behavior for T<T0/3, reflecting the metallic nature of the ordered state. Surprisingly, 1/T1 exhibits a small peak at 10 K, revealing the presence of slow spin fluctuations that may be associated with domain wall motion.

11 pages, 8 figures

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• Evidence for filamentary superconductivity nucleated at antiphase domain walls in antiferromagnetic CaFe${}_2$As${}_2$
• Progressive slowing down of spin fluctuations in underdoped LaFeAsO${}_{1-x}$F${}_x$
• 75As NMR-NQR study in superconducting LiFeAs
• Diluted paramagnetic impurities in nonmagnetic Ba${}_2$YIrO${}_6$
• Spin freezing in the disordered pyrochlore magnet NaCaCo${}_2$F${}_7$: NMR studies and Monte-Carlo simulations
• Antiferromagnetic spin correlations and pseudogap-like behavior in Ca(Fe1-xCox)2As2 studied by 75As nuclear magnetic resonance and anisotropic resistivity
• Effect of proton irradiation on the normal state low-energy excitations of Ba(Fe${}_{1-x}$Rh${}_x$)${}_2$As${}_2$ superconductors
• Phase Separation, Competition, and Volume Fraction Control in NaFe${}_{1-x}$Co${}_x$As
• Persistence of slow fluctuations in the overdoped regime of Ba(Fe1-xRhx)2As2 superconductors
• Spin-3/2 nuclear magnetic resonance: Exact solutions for aligned systems and implications for probing Fe-based superconductors