Spin, charge, and orbital order inMn2OBO3

The magnetic ordering in ${\mathrm{Mn}}_2\mathrm{O}\mathrm{B}{\mathrm{O}}_3$ has been determined from neutron diffraction and magnetization measurements. Long range antiferromagnetic order occurs below $T_N=26\mathrm{K}$, other apparent magnetic transitions are due to secondary phases. The magnetic order has a $\left(\frac{1}{2}0\frac{1}{2}\right)$ propagation vector and the antiferromagnetic spin arrangement has been refined. The low ordering temperature and ordered moment $\left(1.0{\mu }_{\mathrm{B}}\right)$ at the ${\mathrm{Mn}}^{3+}$ sites evidence magnetic frustration arising from the charge and orbital ordered arrangement of ${\mathrm{Mn}}^{2+}$ and Jahn-Teller ${\mathrm{Mn}}^{3+}$ states. This is supported by a qualitative assessment of the Mn-O-Mn superexchange interactions.