Abstract
The magnetic properties of a polycrystalline sample of LuFe2O4 have been investigated by means of magnetization measurements combined with neutron scattering, between 1.5 and 300 K. Magnetic Bragg peaks appear below TN = 240 K and can be indexed in a monoclinic cell, using two propagation vectors, k1 = (0 2/3 0)m and k2 = (0 2/3 1/2)m [or k′2 = (0 2/3 1/6)m], which correspond to either a ferromagnetic or an antiferromagnetic stacking of the [Fe2O4]∞ bilayers. A modeling of possible magnetic structures evidences in addition that the coupling within a bilayer can be either ferromagnetic or antiferromagnetic. Results point out a complex magnetic ground state, which can be understood as coexisting antiferromagnetic and ferrimagnetic phases with a large axial magnetic anisotropy of about 8 meV.