Low temperature evolution of the Faraday rotation in samarium iron garnet

Faraday rotation (FR) measurements performed On single crystal Samarium Iron Garnet (SmIG) at 1.15 µm wavelength are presented under a magnetic field up to 20 kOe applied along the [111] direction in the 10.5-300 K temperature range. At 60 K when the first order magneto-structural phase rotation (
\langle 111 \rangle \rightleftarrow \langle 110 \rangle
) takes place, an abrupt change of the F.R. is observed. The results are analyzed using different theoretical models with a special attention to the crossover point where the Sm
³⁺
sublattice magnetization becomes equal to zero.