Sheveleva, Evgeniia Xu, Bing Marsik, Premysl Lyzwa, Fryderyk Mallett, Benjamin P. P. Willa, K. Meingast, C. Wolf, Th. Shevtsova, T. Pashkevich, Yu. G. Bernhard, Christian 2020 The magnetic and superconducting properties of a series of underdoped Ba 1 − x Na x Fe 2 As 2 (BNFA) single crystals with 0.19 ≤ x ≤ 0.34 have been investigated with the complementary muon-spin-rotation ( μ SR ) and infrared spectroscopy techniques. The focus has been on the different antiferromagnetic states in the underdoped regime and their competition with superconductivity, especially for the ones with a tetragonal crystal structure and a so-called double-Q magnetic order. Besides the collinear state with a spatially inhomogeneous spin-charge-density wave (i-SCDW) order at x = 0.24 and 0.26, that was previously identified in BNFA, we obtained evidence for an orthomagnetic state with a “hedgehog”-type spin vortex crystal (SVC) structure at x = 0.32 and 0.34. Whereas in the former i-SCDW state the infrared spectra show no sign of a superconducting response down to the lowest measured temperature of about 10 K, in the SVC state there is a strong superconducting response similar to the one at optimum doping. The magnetic order is strongly suppressed here in the superconducting state and at x = 0.34 there is even a partial reentrance into a paramagnetic state at T ≪ T c . application/pdf https://folia.unifr.ch/global/documents/309267 https://folia.unifr.ch/documents/309267/files/bernhard_et_al_2020_muon.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevB.101.224515 info:eu-repo/semantics/openAccess License undefined Physical Review B. - 2020, vol. 101, no. 22, p. 224515 High Tc superconductors info:eu-repo/classification/udc/53 Muon spin rotation and infrared spectroscopy study of Ba$_{1-x}$Na$_{x}$Fe$_{2}$As$_{2}$ http://purl.org/coar/resource_type/c_6501