Origin of the unconventional magnetoresistance in Sr ₂ FeMoO ₆

Abstract

The unusual magnetoresistance (MR) behavior in Sr2FeMoO6, recently termed as\nspin-valve type MR (SVMR), presents several anomalies that are little\nunderstood so far. The difficulty in probing the origin of this phenomenon,\narising from the magnetic property of only a small volume fraction of the\nferromagnetic bulk, is circumvented in the present study by the use of ac\nsusceptibility measurements that are sensitive to the slope rather than the\nmagnitude of the magnetization. The present study unravels a spin-glass (SG)\nlike surface layer around each soft ferromagnetic (FM) grain of Sr2FeMoO6. It\nis also observed that there is a very strong exchange coupling between the two,\ngenerating `exchange bias' effect, which consequently creates the `valve',\nresponsible for the unusual MR effects.\n