Anisotropy in the magnetization and magnetoelectric response of single crystalline Mn₄Ta₂O₉

We report temperature dependent magnetization and neutron diffraction measurements on the corundum related magnetoelectric antiferromagnet Mn$_{4}$Ta$_{2}$O$_{9}$. Measurements performed on a single crystalline specimen reveal that the magnetization is anisotropic, and a weak ferromagnetic component emerges well within the antiferromagnetically ordered state. Powder neutron diffraction measurements indicate that the magnetic structure comprises of antiferromagnetically coupled ferromagnetic chains of Mn$^{2+}$ spins aligned along the trigonal $c$ axis, in contrast to that reported in other isostructural members of this family. Magnetic measurements performed under a periodic electric field indicate that the magnetoelectric response is also anisotropic, with this coupling along the trigonal $c$ axis and that perpendicular to it having different signs.