Lattice distortion in TmCo$_2$: a poly- and single- crystal study

Within the RCo$_2$ family of compounds, a structural distortion linked with the onset of magnetic ordering around the critical temperature can be observed. One of the less explored RCo$_2$ compounds is TmCo$_2$ probably due to its low Curie temperature. Exceptionally this compound, given its position at the end of the ferrimagnetic series, shows discrepancies in the ordering of the Co sub-lattice because of a weak Weiss molecular field. In this paper we focus on the structural distortion in TmCo$_2$, which appears together with the magnetic ordering around the critical temperature of $T_{C}\sim3.6$~K. Poly-crystals as well as single-crystals of TmCo$_2$ were used in our experiments. For both kinds of samples we observed the same type of the rhombohedral distortion along the [111] direction from the cubic Fd$\bar{3}$m to R$\bar{3}$m space group. The relation between observed magnetic and structural properties in this compound is discussed.