Growth, properties and magnetism of CaKFe4As4

Abstract

I would like to dedicate this thesis to my parents, Don and Judy Meier, for making science interesting and supporting me along the way. Janet is pretty cool too, I guess. iii

Magnetism and its coexistence with superconductivity in CaK(Fe0.949Ni0.051)4As4Khasanov1, Simutis2, Pashkevich3 et al. 2020Phys. Rev. B9250View full textAdd to dashboardCite

“…CaK(Fe 0.949 Ni 0.051 ) 4 As 4 single crystals were grown from a high-temperature Fe-As rich melt and extensively characterized by thermodynamic and transport measurements [10][11][12][13][14][15]. The selected crystal with dimensions of 4.0 × 4.0 × 0.1 mm 3 was used.…”

“…The Ca ions reside at 1a Wyckoff position (0,0,0), K at the 1d position (0.5,0.5,0.5), Fe at the 4i position (0,0.5,0.76820), As1 at the 2g position (0,0,0.34150), and As2 at the 2h position (0.5,0.5,0.12310). The lattice constants were taken to be a = 3.8659 Å and c = 12.8840 Å [11,12]. The all-electron full-potential linearized augmented planewave method (ELK code) [26], with the local spin-density approximation [27], for the exchange correlation potential and with the revised generalized gradient approximation of Perdew-Burke-Ernzerhof [28] was applied.…”

“…The magnetism was further identified as the hedgehog spin-vortex-crystal (SVC) order, which is characterized by noncollinear Fe moments featuring an alternating all-in and all-out motif around the As1 sites within the ab planes and antiferromagnetic coupling along the c direction [13,15]. In addition, the interplay of magnetism and superconductivity in CaK(Fe 1−x Ni x ) 4 As 4 was clearly detected in NMR, Mössbauer spectroscopy, and neutron scattering experiments [10][11][12][13][14][15][16]. As both states compete for the same electrons at the Fermi surface, the magnetic order parameter was found to be strongly reduced below T c .…”

“…ground state from superconducting to antiferromagnetically (AFM) ordered [11][12][13]. The resistivity and the specific-heat measurements [10][11][12], as well as the Mössbauer [13,14], the nuclear magnetic resonance (NMR) [13], and the neutron scattering studies [15] reveal the appearance of a magnetic order. The magnetism was further identified as the hedgehog spin-vortex-crystal (SVC) order, which is characterized by noncollinear Fe moments featuring an alternating all-in and all-out motif around the As1 sites within the ab planes and antiferromagnetic coupling along the c direction [13,15].…”

“…previously in Refs. [12][13][14][15]. The temperature evolution of the magnetic order parameter m Fe (T ) was analyzed by using the approach of Machida [14,17], accounting for coexistence of a spin-density-wave magnetism and superconductivity.…”