M\"{o}ssbauer Study of Eu$_{14}$MnSb$_{11}$ and Yb$_{14}$MnSb$_{11}$ Zintl Compounds.

Antimony-121 M\"{o}ssbauer effect measurements have been performed mainly on Eu$_{14}$MnSb$_{11}$ and Yb$_{14}$MnSb$_{11}$ zintl compounds, through the temperature range from 2 K to room temperature. The isomer shifts observed (-4.5mm/sec to --10.3 mm/sec and -7.7 mm/sec to --11.2 mm/sec, respectively) from the present study for both Eu$_{14}$MnSb$_{11}$ and Yb$_{14}$MnSb$_{11}$ zintl compounds are close to the values (-8.54mm/sec to --8.73mm/sec) obtained for InSb, the standard compound for antimony-121 M\"{o}ssbauer effect measurements. Isomer shift distribution fits by using a Voigt-based Gaussian distribution profile show distinct peaks at the corresponding average isomer shift values obtained from Lorentzian four-site fits for Eu$_{14}$MnSb$_{11. }$ The study of the temperature dependence of line broadening as well as hyperfine magnetic field confirms the existence of long-range magnetic ordering of antimony-121 in Eu$_{14}$MnSb$_{11 }$below 12 K which resulted in the transition temperature, $T_C $, of 12 K, whereas $T_C $ found in Yb$_{14}$MnSb$_{11}$ is 45 K. The linear fit of the natural logarithm of area versus temperature using the Debye model for the high-temperature limit gives the values of 185 K and 196 K for the Debye temperature for Eu$_{14}$MnSb$_{11 }$and Yb$_{14}$MnSb$_{11}$ zintl compounds, respectively.