Spin excitations in K$_{0.84}$Fe$_{1.99}$Se$_2$ superconductor as studied by M\

  title={Spin excitations in K\$\_\{0.84\}\$Fe\$\_\{1.99\}\$Se\$\_2\$ superconductor as studied by M\},
  author={Zhiwei Li and Xiaoming Ma and Hua Pang and Fashen Li},
M\"ossbauer spectroscopy was used to probe the site specific information of the $K_{0.84}Fe_{1.99}Se_2$ superconductor. Possibility of coexistence of superconductivity and magnetism is discussed. A spin excitation gap, $\Delta E \approx$5\,meV, is observed by analyzing the temperature dependence of the hyperfine magnetic field (HMF) at the iron site within the spin wave theory. Using a simple model suggested in the literature, the temperature dependence of the HMF is well reproduced, suggesting… Expand
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