Abstract
A new method for the preparation of Mn3 11B7O13I powder sample, used for neutron diffraction, is presented. Magnetization measurements on powder samples of Mn3B7O13X (X=C1, Br, I) have shown that their Néel temperatures are 11±0.5 K for Mn3B7O13Cl, 14±0.5 K for Mn3B7O13Br and 26±0.5 K for Mn3B7O13I. The crystal and the magnetic structures of Mn3B7O13I have been investigated by neutron diffraction. The neutron diffraction pattern in the paramagnetic phase at 35 K was refined in space group Pca211′. The neutron diffraction data confirm the onset of magnetic ordering at 26 K. The magnetic structure has been determined at 1.5 K in the magnetic space group Pc′a21′. The magnetic moments of the three manganese sites order with a two-dimensional canted spin arrangement. The moments of two sites point along c with μz(Mn2) = μz(Mn3) = 3.8(2) μ B /atom while the Mn(l) site has a magnetic moment of 5.4(2) μ B /atom located in the (101) orthorhombic plane, forming an angle of 12.0(3) degrees with the a direction. The effect of the antiferromagnetic/ferromagnetic compromise on the Mn—I—Mn pathways is discussed.