Magnetic properties of a highly ordered single crystal of the layered perovskite YBaCuFe0.95Mn0.05O5

•The high-quality single crystal was grown by a modified TSFZ method.•The structural and magnetic properties of the single crystal have been solved by using the neutron diffraction.•The magnetic phases and transitions found in the crystal are fully described and analyzed in the light of its high level of Fe/Cu cationic order.•The result gives strong support to the “order by disorder” theoretical models intended to justify the high-temperature stability of the spiral phase.