Nonmagnetic ions enhance magnetic order in the ludwigite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Co</mml:mtext><mml:mn>5</mml:mn></mml:msub><mml:mtext>Sn</mml:mtext><mml:mo>(</mml:mo><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>BO</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

The ludwigite ${\text{Co}}_{5}\text{Sn}({\mathrm{O}}_{2}{\text{BO}}_{3}{)}_{2}$ was studied using x-ray diffraction, M\"ossbauer 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.