Large magnetoresistance in double perovskite Sr2Cr1.2Mo0.8O6-δ

Sr2Cr1.2Mo0.8O6-delta (delta =0, 0.2) with a double perovskite structure was prepared by solid state reaction in evacuated quartz tubes. Cr and Mo are partially ordered on the B site. Oxygen vacancies decrease the ordering, but: increase the lattice parameters. X-ray absorption spectroscopy results are consistent with Cr being 3+, and Mo being close to 5+ for delta = 0.2 and 5.5 for delta = 0. The spin of Cr3+ (d(3)) and Mo5+ (d(1)) order in an anti-parallel arrangement by superexchange interaction, and lead to ferrimagnetic ordering below 465 K, Both compounds are n-type narrow gap semiconductors. Large magnetoresistance (-43%) is observed in Sr2Cr1.2Mo0.8O6. The MR behavior is attributed to an intra-grain tunneling mechanism. (C) 2001 Elsevier Science Ltd. All rights reserved.