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arXiv · 1209.6271

Temperature dependence of the paramagnetic spin excitations in BaFe$_2$As$_2$

Leland W. Harriger·Mengshu Liu·Huiqian Luo·R. A. Ewings·C. D. Frost·T. G. Perring·Pengcheng Dai
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Abstract

We use inelastic neutron scattering to study temperature dependence of the paramagnetic spin excitations in iron pnictide BaFe$_2$As$_2$ throughout the Brillouin zone. In contrast to a conventional local moment Heisenberg system, where paramagnetic spin excitations are expected to have a Lorentzian function centered at zero energy transfer, the high-energy ($\hbar\omega>100$ meV) paramagnetic spin excitations in BaFe$_2$As$_2$ exhibit spin-wave-like features up to at least 290 K ($T= 2.1T_N$). Furthermore, we find that the sizes of the fluctuating magnetic moments $ \approx 3.6\ \mu^2_B$ per Fe are essentially temperature independent from the AF ordered state at $0.05T_N$ to $2.1T_N$, which differs considerably from the temperature dependent fluctuating moment observed in the iron chalcogenide Fe$_{1.1}$Te [I. A. Zaliznyak {\it et al.}, Phys. Rev. Lett. {\bf 107}, 216403 (2011).]. These results suggest unconventional magnetism and strong electron correlation effects in BaFe$_2$As$_2$.

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Leland W. Harriger, Mengshu Liu, Huiqian Luo, R. A. Ewings, C. D. Frost, T. G. Perring, Pengcheng Dai. 2012-09-27. Temperature dependence of the paramagnetic spin excitations in BaFe$_2$As$_2$. https://doi.org/10.1103/physrevb.86.140403

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