Magnetic ordering in manganites substituted by chromium ions

NdMn1-xCrxO3 and Nd0.6Ca0.4Mn1-xCrxO3 solid solutions have been studied by neutron diffraction and magnetic measurements. NdMn0.5Cr0.5O3 is found to have a magnetic structure consisting of an antiferromagnetic G-type component and a ferromagnetic component, which are caused by 3d ions. The magnetic moments of the neodymium ions are parallel to the ferromagnetic component. Nd0.6Ca0.4Mn0.5Cr0.5O3 mainly has a G-type magnetic structure, and the magnetic moments of the neodymium ions are normal to the antiferromagnetism vector. Magnetic phase diagrams are plotted for both systems. They are interpreted on the assumption that the Mn3+-O-Cr3+ superexchange interactions are positive and the Mn4+-O-Cr3+ interactions are negative; the fact that manganese and chromium ions are not ordered in a crystal lattice is taken into account. Concentration magnetic phase transformations proceed through a two-phase state because of the internal chemical inhomogeneity of the solid solutions