Colossal magnetoresistance

About: Colossal magnetoresistance is a research topic. Over the lifetime, 3658 publications have been published within this topic receiving 130104 citations.

Transport properties of Na doped La1−xCax−yNayMnO3 measured in a pulsed magnetic field

Abstract: Temperature-dependent magnetization and magnetoresistance of the Na doped La1−x Cax−y NayMnO3 type samples withx = 0. 3a nd 0 y 0.15, showing a rhombohedrally distorted perovskite structure with space group R ¯ 3c ,h av eb een

Low-temperature magnetoresistance in insulating a-Gd x Si 1-x alloys

Abstract: We report on low-temperature magnetotransport measurements on the amorphous semiconductor $a\ensuremath{-}{\mathrm{Gd}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}$ with $x\ensuremath{\sim}0.13,$ on the insulating side of the $T=0$ metal-insulator transition for this material. The samples exhibit a negative magnetoresistance of more than five orders of magnitude at 1 K, which grows exponentially larger at lower temperatures. The temperature dependence of the conductivity displays an activated form indicative of variable range hopping in the presence of a Coulomb gap in all magnetic fields from 0 to 9 T, while the characteristic temperature ${T}_{0}$ of the hopping conductivity decreases from over 300 K in 0 T to 6 K in 8.5 T. This enormous magnetoresistance must arise from an exchange interaction between the conduction electrons and the local Gd moments which are randomly oriented in zero field and become (partially) aligned in 9 T, and its consequent influence on the electron-electron interaction. However, it remains to be determined whether the effect of this magnetic interaction is a relative shift of the Fermi energy relative to the mobility edge and a modification to the Coulomb gap or a change in the bandwidth and its consequent effect on the electronic density of states.

Magnon Broadening Effect by Magnon-Phonon Interaction in Colossal Magnetoresistance Manganites

Abstract: In order to study the magnetic excitation behaviors in colossal magnetoresistance manganites, a magnon-phonon interacting system is investigated. Sudden broadening of magnon linewidth is obtained when a magnon branch crosses over an optical phonon branch. Onset of the broadening is approximately determined by the magnon density of states. Anomalous magnon damping at the brillouine zone boundary observed in low Curie temperature manganites is explained.

Conductivity and magnetoresistance of hydrogenated amorphous silicon-nickel alloys near the metal-insulator transition

Abstract: The authors present conductivity and magnetoresistance data for a range of a-Si1-yNiy:H alloys near the metal-insulator transition. In the metallic regime, weak-localization and interaction effects are identified, the latter being of normal sign. In the activated regime, conductivity results imply variable-range hopping in a parabolic density of states but quantitative analysis shows that if this density of states results from a Coulomb gap then the localized states extend over large clusters of nickel atoms. The magnetoresistance data generally show positive magnetoresistance attributed to spin splitting in interaction effects, but negative magnetoresistance attributed to suppression of weak-localization-type interference, is seen on the insulating side of the transition at not too low temperatures where interaction effects are partially suppressed.