Influence of Fe-site substitutions upon intragrain and intergrain magnetoresistance in the double-perovskite Ba2FeMoO6

Transport and magnetic properties are significantly influenced by the subst itution of various divalent (Mg, Zn, Ca) and trivalent (Cr, Mn, In, Y) cati ons for iron in the double-perovskite Ba2FeMoO6. An increase of the resisti vity and a spectacular decrease of ferromagnetism, especially of Tc, are ob served as the substitution level increases. Both intragrain magnetoresistan ce (MR), characterized by a peak of the resistance ratio around Tc, and int ergrain tunnel magnetoresistance (TMR), at low temperature, are observed. T he substitution does not kill the TMR because the TMR effect is obtained fo r the substitution level as high as 40% on the Fe site. More importantly, h igh TMR magnitudes are observed for zinc-substituted oxides.