Large magnetoresistance and Jahn-Teller effect in Sr2FeCoO6

• Published in: The European physical journal. B, Condensed matter physics Condensed matter physics, 2012-08, Vol.85 (8), Article 260
• Main Authors: Pradheesh, R., Nair, Harikrishnan S., Sankaranarayanan, V., Sethupathi, K.
• Format: Article
• Language: English
• Subjects: Complex Systems; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fluid- and Aerodynamics; Giant magnetoresistance; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Magnetotransport phenomena, materials for magnetotransport; Mössbauer effect; other γ-ray spectroscopy; Physics; Physics and Astronomy; Regular Article; Solid State Physics
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2012-30264-2

Neutron diffraction measurement on the spin glass double perovskite Sr 2 FeCoO 6 reveals site disorder as well as Co 3+ intermediate spin state. In addition, multiple valence states of Fe and Co are confirmed through Mössbauer and X-ray photoelectron spectroscopy. The structural disorder and multiple valence lead to competing ferromagnetic and antiferromagnetic interactions and subsequently to a spin glass state, which is reflected in the form of an additional T -linear contribution at low temperatures in specific heat. A clear evidence of Jahn-Teller distortion at the Co 3+ –O 6 complex is observed and incorporating the physics of Jahn-Teller effect, the presence of localized magnetic moment is shown. A large, negative and anomalous magnetoresistance of  ≈63% at 14 K in 12 T applied field is observed for Sr 2 FeCoO 6 . The observed magnetoresistance could be explained by applying a semi-empirical fit consisting of a negative and a positive contribution and show that the negative magnetoresistance is due to spin scattering of carriers by localized magnetic moments in the spin glass phase.