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The recent discovery of the proximity of the antiferromagnetism and superconductivity in iron pnictides strongly enhanced the interest to the spin fluctuations in antiferromagnets. We report the theoretical study of the spin-flip excitations in FeRh. This system is antiferromagnetic (AFM) in the ground state and experiences the transition in the ferromagnetic (FM) state at 370 K that allows the comparison of the excitations in AFM and FM phases of the same material. For completeness, also the spin-flip excitations in paramagnetic Rh are considered. The study is based on the calculation of the transversal magnetic susceptibility within the framework of the time dependent density functional theory. Among topics we discuss are (i) non-monotonous wave-vector dependence of the attenuation of AFM magnons, (ii) induction of the spin moments of Rh atoms by the AFM magnons, (iii) small attenuation of the acoustic FM magnons in contrast to the strong damping of the optical magnons, (IV) different chirality properties of the AFM magnons, FM magnons and paramagnons. We suggest a coherent picture of the excitations in different systems based on the analysis of the electron structure and spectral density of Stoner excitations. |
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