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

Sr2Cr1.2Mo0.8O6-δ (δ=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 δ = 0.2 and 5.5 for δ = 0. The spin of Cr3+ (d3) and Mo5+ (d1) 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.