Itinerant Magnetic Excitations in AntiferromagneticCaFe2As2

Abstract

Neutron scattering measurements of the magnetic excitations in single crystals of antiferromagnetic CaFe2As2 reveal steeply dispersive and well-defined spin waves up to an energy of approximately 100 meV. Magnetic excitations above 100 meV and up to the maximum energy of 200 meV are however broader in energy and momentum than the experimental resolution. While the low energy modes can be fit to a Heisenberg model, the total spectrum cannot be described as arising from excitations of a local moment system. Ab initio calculations of the dynamic magnetic susceptibility suggest that the high energy behavior is dominated by the damping of spin waves by particle-hole excitations.

Neutron studies of the iron-based family of high TC magnetic superconductors

“…For the undoped materials the spin wave dispersion relations have been measured for the SrFe 2 As 2 [40], CaFe 2 As 2 [41,42], and BaFe 2 As 2 [43,44] systems, and the overall spin dynamics for the three systems are quite similar as shown in Table 3. These studies reveal that the spin dynamics are quite energetic, with a spin wave bandwidth ~0.2 eV as shown in Fig.…”

“…Obviously these first experimental results will be refined as the measurements are extended, but the basic energetics are now known. At high energies the spin waves are reported to be heavily damped [42], as can occur for itinerant electron systems where the collective excitations interact with the single-particle density of states. We would also expect that the overall spin dynamics for the 1:1:1:1 systems will be similar, but at the present time sizable single crystals are not available and little work has been carried out [15].…”

Weak spin interactions in Mott insulating La2O2Fe2OSe2McCabe1, Stock2, Rodriguez3 et al. 2014Phys. Rev. B4527630View full textAdd to dashboardCite

“…Analogous to the cuprates, the spin exchange constants and spin-wave dispersions in these parent compounds are large, extending up to energy transfers of ∼100 meV, reflecting strong Fe-Fe coupling [19][20][21][22][23][24]. Electronic structure calculations for La 2 O 2 Fe 2 OSe 2 suggest similar exchange constants to the pnictides but with considerable electronic band narrowing [14].…”

Absence of localized-spin magnetism in the narrow-gap semiconductor FeSb2

“…[16][17][18] Many of the unique electronic properties which are of great current and future technological interest are intertwined with the emerging magnetism in these materials. Recent discovery of the new variety of the high-temperature superconductivity in layered transition metal pnictides, which is also closely related with magnetism, [19][20][21][22][23][24][25] has generated new surge of interest in the physical properties of these compounds.…”