Magnetic phase transitions in samarium iron garnet

Mössbauer spectroscopy has shown that there are at least three magnetic phases of samarium iron garnet and possibly five, if spin reorientations that are not abrupt are assumed to occur between these phases. The easy magnetic axes are: [111], $560>T\gtrsim 60$ K; [110], $\sim 45>T\gtrsim 18$ K; [100], $\sim 10>T>~5$ K. The spin reorientations are estimated to occur between ∼60 and ∼45 K and between ∼18 and ∼10 K. While the phases with the [111] and [110] easy magnetic axis have been reported before, this is the first report of the lowest-temperature phase with [100] easy magnetic axis, and of the possible spin reorientations. If the latter exist, the lowest-temperature phase cannot be tetragonal; it is most likely orthorhomic. The sequence of magnetic space groups is: $R\overline{3}{c}^{\prime },\left[111\right]\mathrm{}\to \frac{F{2}^{\prime }}{d^{\prime }}\to \mathrm{Fd}{d}^{\prime }{d}^{\prime }$, $\mathrm{}\left[110\right]\mathrm{}\to \frac{I{2}^{\prime }}{c^{\prime }}\to \mathrm{Ib}{c}^{\prime }{a}^{\prime },\mathrm{}\left[100\right]\mathrm{}$.