Magnetic fluctuations and spin freezing in nonsuperconducting LiFeAs derivatives

Abstract

We present detailed magnetometry and muon-spin rotation data on polycrystalline samples of overdoped, non-superconducting LiFe${}_{1-x}$Ni${}_x$As ($x=0.1,0.2$) and Li${}_{1-y}$Fe${}_{1+y}$As ($0\le y\le 0.04$) as well as superconducting LiFeAs. While LiFe${}_{1-x}$Ni${}_x$As exhibits weak antiferromagnetic fluctuations down to $1.5\mathrm{K}$, Li${}_{1-y}$Fe${}_{1+y}$As samples, which have a much smaller deviation from the $1:1:1$ stoichiometry, show a crossover from ferromagnetic to antiferromagnetic fluctuations on cooling and a freezing of dynamically fluctuating moments at low temperatures. We do not find any signatures of time-reversal symmetry breaking in stoichiometric LiFeAs that would support recent predictions of triplet pairing.

5 pages, 4 figures

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• Correlation-enhanced odd-parity inter-orbital singlet pairing in the iron-pnictide superconductor LiFeAs
• Hund's metal crossover and superconductivity in the 111 family of iron-based superconductors
• Small and nearly isotropic hole-like Fermi surfaces in LiFeAs detected through de Haas van Alphen-effect
• The Three-Dimensional Electronic Structure of LiFeAs: Strong-coupling Superconductivity and Topology in the Iron Pnictides
• Microscopic origin of ultranodal superconducting states in spin-1/2 systems
• Defect states in LiFeAs as seen by low temperature scanning tunneling microscopy and spectroscopy
• Absence of hexagonal to square structural transition in LiFeAs vortex matter
• Hole-$s_{\pm }$ State Induced by Coexisting Ferro- and Aniferromagnetic and Aniferro-orbital Fluctuations in the Iron Pnictides
• Absence of nematic instability in LiFeAs