Mössbauer study of Brownian motion of FeSn${\mathrm{O}}_3$ particles in liquid-crystal N-($p$-ethoxybenzylidene)-$p^{\prime }$-butylaniline (EBBA)

The effects of Brownian motion of small particles of FeSn${\mathrm{O}}_3$ in liquid-crystal EBBA on 14.4-keV ${\mathrm{Fe}}^{57}$ and 23.8-keV ${\mathrm{Sn}}^{119}$ Mössbauer spectra in the temperature range 300 - 360 K are reported. Mössbauer spectral lines begin to broaden a few degrees below the solid → nematic phase-transition temperature. In the nematic range and in the isotropic liquid region, except very close to the nematic → isotropic phase-transition temperature, the line broadening ($\Delta E-\Gamma$) is linearly proportional to $\frac{T}{\eta }$. There is an anomalous change in the line broadening at and near the nematic → isotropic phase-transition temperature. The area under resonance sharply decreases at the solid → nematic phase transition. In the nematic and in the isotropic region, line broadening is associated with decrease in recoilless fraction.