Magnetism and CMR in electron doped perovskite and layered manganites

From the magnetic phase diagrams established for Ln(1-x)AE(x)MnO(3) manganites with x > 0.5, it is shown that the magnetoresistance is only obtained for compositions of smallest average A-site cations <r(A)>. The magnetic structure study reveals that the small <r(A)> favors the coexistence of ferromagnetism with G-type antiferromagnetism. It is also shown that ferromagnetism can be induced in the Ln(2-x)AE(x)MnO(4) type electron doped manganites by using compositions with small Ln and AE cations and x values close to 1.90. Finally, manganse site doping by Cr, Co, Ni can be used to weaken the charge-ordering of the Mn4+ rich perovskite manganites (0.5 < x less than or equal to 0.8) and thus to induce CMR properties.