The ludwigite ${\text{Co}}_5\text{Sn}({\mathrm{O}}_2{\text{BO}}_3{)}_2$ was studied using x-ray diffraction, Mössbauer spectroscopy, and magnetic and thermodynamic measurements. This material belongs to a family of oxyborates which presents low-dimensional subunits in the form of three-leg ladders in its structure. The subunits confer to these materials a strong anisotropy in their exchange interactions that provide to the ludwigites several interesting magnetic properties, from partial ordering to spin-glass states. Despite being doped by nonmagnetic ions, ${\text{Co}}_5\text{Sn}({\mathrm{O}}_2{\text{BO}}_3{)}_2$ has long-range magnetic order below 82 K which is, surprisingly, the highest critical temperature found so far in the ludwigites. This record can be explained by the absence of double-exchange interactions, usually present in the ludwigites and that gives rise to strong competition. In this paper we study the magnetic and structural properties of ${\text{Co}}_5\text{Sn}({\mathrm{O}}_2{\text{BO}}_3{)}_2$ and compare our results with those obtained in other cobalt ludwigites.

• Received 29 November 2014
• Revised 19 January 2015

DOI:https://doi.org/10.1103/PhysRevB.91.054402