Eur. Phys. J. B (2012) 85: 260
https://doi.org/10.1140/epjb/e2012-30264-2

Regular Article

Large magnetoresistance and Jahn-Teller effect in Sr₂FeCoO₆

¹ Low Temperature Physics Laboratory, Department of Physics, Indian Institute of Technology Madras, 600036 Chennai, India
² Jülich Center for Neutron Sciences 2/ Peter Grünberg Institute 4, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

^a e-mail: rpradeesh@physics.iitm.ac.in

Received: 27 March 2012
Received in final form: 29 May 2012
Published online: 30 July 2012

Abstract

Neutron diffraction measurement on the spin glass double perovskite Sr₂FeCoO₆ reveals site disorder as well as Co³⁺ 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 Co³⁺–O₆ 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 Sr₂FeCoO₆. 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.