We report complex dielectric and Raman spectroscopy measurements in hematite crystallites, which are either hexagon-shaped plates or cuboids. Temperature variation of magnetization data in all these samples exhibits sharp Morin transition (T _M ). Moderate but clear enhancement in the real part of the dielectric constant is observed in the vicinity of the T _M in all the samples. However a relaxation-like behavior in the imaginary part is observed only in nanoplates or big cuboids across the T _M . The real part of the dielectric constant fits well to the modified-Barrett equation above T _M (in the spin-canted region), whereas clear deviations are observed below T _M (in the pure antiferromagnetic region). The frequency of the phonon mode, deduced from the Barrett fitting, matches with the E _u Raman mode of hematite. Temperature-dependent Raman spectra reveal anomalies in all major phononic modes in the vicinity of the T _M . Anharmonic fitting of the temperature-dependent Raman and modified-Barrett fitting of the dielectric data brings forward modifications in spin-phonon coupling in the vicinity of the Morin transition temperature in hematite.

我们报告了赤铁矿微晶的复杂介电和拉曼光谱测量，它们是六边形板或长方体。在所有这些样品表现出尖锐Morin转换（磁化数据的温度变化Ť _中号）。在所有样品的T _M附近观察到介电常数实部的适度但明显的增强。然而，仅在跨越T _{M 的}纳米板或大长方体中观察到虚部中的类似松弛行为。介电常数的实部与T _M以上的修正 Barrett 方程非常吻合 （在自旋倾斜区域），而在T _M以下（在纯反铁磁区域）观察到明显的偏差。从 Barrett 拟合推导出的声子模式的频率与赤铁矿的E _u拉曼模式匹配。温度相关的拉曼光谱揭示了T _M附近所有主要声子模式的异常。温度相关拉曼的非谐波拟合和介电数据的修正巴雷特拟合提出了赤铁矿莫林转变温度附近自旋声子耦合的修正。