Antisite-defects vs grain boundaries competition in the magnetoresistance of the Sr_2FeMoO6 double perovskite
Abstract
It has been shown that the tunneling magnetoresistance (TMR) in the Sr_2FeMoO6 compound can be readily improved by selected oxidation of the grain boundaries (gb's). However, the role of the antisite-defects (AS) which occur inside the grains is far from clear. AS appear due to the exchange of the crystallographic positions of Fe and Mo ions in the B site of the ordered perovskite, giving rise to a reduction in the saturation magnetization (M_S) due to antiferromagnetic Fe-Fe interactions. Here we present magnetotransport data on two samples with different concentrations of AS (w ∼ 0.3 and 0.1). We performed several oxidation processes on these samples and studied the evolution of the magnetization and TMR. While MS remained unchanged, the resistivity (ρ) was increased by more than 5 orders of magnitude after oxidation, showing the importance of the gb's. At the same time, at low ρ values the TMR is much higher in the less disordered sample (w ∼ 0.1). On the contrary, when the gb's dominate in the transport properties both samples exhibit the same improved TMR values.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MAR.C1077N