Anomalous magnetoresistance in [ Sr2Bi2-xPbxO4] RS[ CoO2] y (x = 0, 0.3, and 0.4; y ≈ 1.85) single crystals

Abstract

Magnetoresistance (MR) of the [ Sr2Bi2-xPbxO4] RS[ CoO2] y (x = 0, 0.3, and 0.4; y ≈ 1.85; RS is referred to rocksalt block) single crystals is investigated systematically. A nonmonotonic variation of the isothermal in-plane and out-of-plane MR with the field is observed. The out-of-plane MR is positive at high temperatures and increases with decreasing T, and exhibits a pronounced hump, then changes the sign from positive to negative at a certain temperature. These results strongly suggest that the observed MR consists of two contributions: one negative and one positive component. The isothermal MR in high magnetic fields follows a H2 law. The negative contribution comes from spin scattering of carriers by localized-magnetic-moments based on the Khosla-Fischer model.