Large intragrain magnetoresistance above room temperature in the double perovskite Ba2FeMoO6

Large intragrain magnetoresistance (MR) in the ordered double perovskite, Ba2FeMo6, is shown for the first time. The latter appears near T-C (340 K), i.e., above room temperature. This effect originates from a double-exchange-like mechanism, based on antiferromagnetic coupling of localized high spin 3d(5)Fe(3+), and itinerant 4d(1) Mo5+ species. Besides this bulk MR, low field tunneling MR at lower temperatures (T < 250 K), due to grain boundary effects, is also observed with large values of MR comparable to those previously observed for Sr2FeMoO6. Such a coexistence of both effects, intragrain and intergrain magnetoresistance, might extend to all members of this double perovskite family, suggesting the possibility of optimizing the MR for working at room temperature in a low magnetic field, by tuning the T-C of solid solutions of such perovskites, (C) 1999 Academic Press.