Oxygen-induced grain boundary effects on magnetotransport properties of Sr2FeMoO6¿d

D. NIEBIESKIKWIAT; A. CANEIRO; D.M. SANCHEZ; J. FONTCUBERTA

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2001 vol. 64 p. 18406 - 18410

1098-0121

The magnetic, electric, and structural properties of polycrystalline samples of Sr2FeMoO61d with controlledoxygen content have been investigated for nominal values d50 and 0.04. We found that the magnetization andlattice parameters are the same in both samples, while the electric properties are drastically affected. Thisbehavior shows that the difference in the oxygen contents is localized in a region near the surface of the grains,thus changing the transport properties of the grain boundaries ~gb’s!. The sample with d50.04 presents aresistivity (r ) that exceeds in more than two orders of magnitude the r for d50. Also the low-field magnetoresistanceis enhanced in ´40% for d50.04 and the voltage-current characteristics present appreciablenonlinearities. We discuss these results in terms of a reinforced tunneling barrier due to the formation of animpurity phase at the gb’s.