Doping dependence of spin dynamics in electron-dopedBa(Fe1−xCox)2

Abstract

The spin dynamics in single crystal, electron-doped Ba͑Fe 1−x Co x ͒ 2 As 2 has been investigated by inelastic neutron scattering over the full range from undoped to the overdoped regime. We observe damped magnetic fluctuations in the normal state of the optimally doped compound ͑x = 0.06͒ that share a remarkable similarity with those in the paramagnetic state of the parent compound ͑x =0͒. In the overdoped superconducting compound ͑x = 0.14͒, magnetic excitations show a gaplike behavior, possibly related to a topological change in the hole Fermi surface ͑Lifshitz transition͒ while the imaginary part of the spin susceptibility Љ prominently resembles that of the overdoped cuprates. For the heavily overdoped, nonsuperconducting compound ͑x = 0.24͒ the magnetic scattering disappears, which could be attributed to the absence of a hole Fermi-surface pocket observed by photoemission.

Doping evolution of spin fluctuations and their peculiar suppression at low temperatures in Ca(Fe1−xCox)2As2Sapkota1, Das2, Böhmer3 et al. 2018Phys. Rev. B72120View full textAdd to dashboardCite

“…The decrease in χ (Q stripe ,E) at low energies contrasts with previous results for the T-PM states of CaFe 2 As 2 [38] and Ba(Fe 1−x Co x ) 2 As 2 [40,48], where χ (Q stripe ,E) generally increases with decreasing temperature. In the T-PM phases of CaFe 2 As 2 [38] and Ba(Fe 1−x Co x ) 2 As 2 [40,48], the magnetic-correlation length in the ab plane increases with decreasing temperature, whereas we find it to be relatively unchanged for Ca(Fe 0.97 Co 0.03 ) 2 As 2 .…”

“…In the T-PM phases of CaFe 2 As 2 [38] and Ba(Fe 1−x Co x ) 2 As 2 [40,48], the magnetic-correlation length in the ab plane increases with decreasing temperature, whereas we find it to be relatively unchanged for Ca(Fe 0.97 Co 0.03 ) 2 As 2 . We find that the decrease of χ (Q stripe ,E) at low energies with decreasing temperature for Ca(Fe 0.97 Co 0.03 ) 2 As 2 is associated with a decrease in the magnitude of the fluctuating Fe moment.…”

Transition from antiferromagnetism to superconductivity in the compensated metallic state ofBa1−xKx(FeSuzuki1, Ohgushi2, Kiuchi3 et al. 2010Phys. Rev. B92171View full textAdd to dashboardCite

“…This is in stark contrast to Ba͑Fe 1−y Co y ͒ 2 As 2 , where the antiferromagentic fluctuations are largely smeared out when the superconductivity disappears. 30,31 This contrasting behavior is likely to be related to the differences in the Fermi surface. In Ba͑Fe 1−y Co y ͒ 2 As 2 , most of the hole Fermi surfaces disappear in the vicinity of the superconductorparamagnetic metal transition 12 whereas there are hole and electron Fermi surfaces with a nesting character in Ba 1−x K x ͑Fe 1−y Co y ͒ 2 As 2 with x =2y.…”

Spin dynamics in electron-doped iron pnictide superconductors

“…Recently, several neutron-scattering ͑NS͒ experiments have been carried out to probe the spin dynamics in these materials, [4][5][6][8][9][10][11][12][13][14][15] and the spin excitation spectrum was fitted by using a J 1 , J 2 Heisenberg model based on localized spins. 8,9,15,16 However while the parent compounds of the cuprates are Mott insulators with large in-plane exchange interactions, 17 the parent iron arsenides are bad metals and remain itinerant at all doping levels.…”