Topic
Colossal magnetoresistance
About: Colossal magnetoresistance is a research topic. Over the lifetime, 3658 publications have been published within this topic receiving 130104 citations.
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TL;DR: The present quantitative description of resistivity is obtained without any fitting parameters, by using the experimental resistivities far away from the transition and the experimental magnetization, and is essentially model-independent.
Abstract: Pairing of oxygen holes into heavy bipolarons in the paramagnetic phase and their magnetic pair breaking in the ferromagnetic phase (the so-called current-carrier density collapse) has accounted for the first-order ferromagnetic-phase transition, colossal magnetoresistance, isotope effect, and pseudogap in doped manganites. Here we propose an explanation of the phase coexistence and describe the magnetization and resistivity of manganites near the ferromagnetic transition in the framework of the current-carrier density collapse. The present quantitative description of resistivity is obtained without any fitting parameters, by using the experimental resistivities far away from the transition and the experimental magnetization, and is essentially model-independent.
61 citations
TL;DR: In this article, the effect of Mn site substitution by Co and Cr on the magnetotransport properties of ceramic samples was systematically investigated as a function of doping, and the existence of an optimum doping level that enhances magnetoresistance was also found.
Abstract: In this paper we show the effect of Mn site substitution $(l~10%)$ by Co and Cr on the magnetotransport properties of ceramic samples of ${\mathrm{La}}_{2/3}{\mathrm{Ca}}_{1/3}{\mathrm{MnO}}_{3}.$ Resistivity, magnetization, and magnetoresistance were systematically investigated as a function of doping. An increase in resistivity and a diminution of metal-insulator transition and Curie temperatures was observed as a consequence of both Co and Cr doping. The evolution of the number of neighbors ferromagnetically coupled to Mn was studied in each sample, and the results suggest some degree of ferromagnetic coupling between ${\mathrm{Cr}}^{3+}$ and Mn ions. Implications of both ferromagnetic Cr ${}^{3+}\ensuremath{-}\mathrm{O}\ensuremath{-}{\mathrm{Mn}}^{3+}$ superexchange and double exchange interactions are discussed. We also found the existence of an optimum doping level that enhances colossal magnetoresistance. This has been explained considering electron localization due to magnetic disorder induced by doping in the Mn site.
61 citations
TL;DR: In this paper, the authors present neutron-diffraction data which show that the magnetic structure of this material switches from antiferromagnetic stacking of the (ferromagnetically ordered) sheets in zero field to ferromagnetic stack in a field of 1.5 T. The data are the first to be collected on any manganite as a function of applied field, exactly as the magnetoresistance data themselves are collected.
Abstract: The layered compound ${\mathrm{La}}_{2\ensuremath{-}2x}{\mathrm{Sr}}_{1+2x}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ $(x=0.3)$ consists of bilayers of metallic ${\mathrm{MnO}}_{2}$ sheets separated by insulating material. The compound exhibits markedly anisotropic magnetoresistance at temperatures well below the three-dimensional magnetic ordering temperature ${T}_{c}=90\mathrm{K}$ in addition to colossal magnetoresistance around ${T}_{c}.$ We present neutron-diffraction data which show that the magnetic structure of this material switches from antiferromagnetic stacking of the (ferromagnetically ordered) sheets in zero field to ferromagnetic stacking in a field of 1.5 T. To our knowledge, the data are the first to be collected on any manganite as a function of applied field, exactly as the magnetoresistance data themselves are collected. They provide a natural explanation of the low-field magnetoresistance in the ordered phase in terms of spin-polarized tunneling between the magnetic layers and suggest that the material is a bulk stack of spin-valve devices.
61 citations
TL;DR: In this paper, soft X-ray magnetic circular dichroism (SXMCD) measurements are reported on the O K and Mn L-absorption edges of La 1− x Sr x MnO 3 ( x = 0.15, 0.18, and 0.4) single crystals in their ferromagnetic regime.
61 citations
TL;DR: In this article, it was shown that these ceramics become magnetically harder when reducing the particle size, exhibiting large magnetic anisotropy that also increases with the grain size, in concomitance with this enhancement of the magnetic hardness a gradual increase of the low-field magnetoresistance is also detected.
Abstract: The low-field magnetoresistance and the magnetization of ceramic oxides have been studied as a function of the grain size. It is shown that these ceramics become magnetically harder when reducing the particle size, exhibiting large magnetic anisotropy that also increases when reducing the grain size. In concomitance with this enhancement of the magnetic hardness a gradual increase of the low-field magnetoresistance is also detected. We suggest that both phenomena are closely related and associated with the existence of some degree of spin disorder at the grain boundaries. Implications of these findings for improvements of the field response sensitivity of these materials are discussed.
61 citations