Colossal magnetoresistance

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

Bridging Structural Inhomogeneity to Functionality: Pair Distribution Function Methods for Functional Materials Development.

Abstract: The correlation between structure and function lies at the heart of materials science and engineering. Especially, modern functional materials usually contain inhomogeneities at an atomic level, endowing them with interesting properties regarding electrons, phonons, and magnetic moments. Over the past few decades, many of the key developments in functional materials have been driven by the rapid advances in short-range crystallographic techniques. Among them, pair distribution function (PDF) technique, capable of utilizing the entire Bragg and diffuse scattering signals, stands out as a powerful tool for detecting local structure away from average. With the advent of synchrotron X-rays, spallation neutrons, and advanced computing power, the PDF can quantitatively encode a local structure and in turn guide atomic-scale engineering in the functional materials. Here, the PDF investigations in a range of functional materials are reviewed, including ferroelectrics/thermoelectrics, colossal magnetoresistance (CMR) magnets, high-temperature superconductors (HTSC), quantum dots (QDs), nano-catalysts, and energy storage materials, where the links between functions and structural inhomogeneities are prominent. For each application, a brief description of the structure-function coupling will be given, followed by selected cases of PDF investigations. Before that, an overview of the theory, methodology, and unique power of the PDF method will be also presented.

Magnons in ferromagnetic metallic manganites.

Abstract: Ferromagnetic (FM) manganites, a group of likely half-metallic oxides, are of special interest not only because they are a testing ground for the classical double-exchange interaction mechanism for the 'colossal' magnetoresistance, but also because they exhibit an extraordinary arena of emergent phenomena. These emergent phenomena are related to the complexity associated with strong interplay between charge, spin, orbital, and lattice. In this review, we focus on the use of inelastic neutron scattering to study the spin dynamics, mainly the magnon excitations in this class of FM metallic materials. In particular, we discuss the unusual magnon softening and damping near the Brillouin zone boundary in relatively narrow-band compounds with strong Jahn-Teller lattice distortion and charge-orbital correlations. The anomalous behaviours of magnons in these compounds indicate the likelihood of cooperative excitations involving spin and lattice as well as orbital degrees of freedom.

Colossal magnetoresistance in cluster glass-like insulator La0.67Sr0.33(Mn0.8Ni0.2)O3

Abstract: Substitution of Ni for Mn in La067Sr033MnO3 (LSMO) lowers the Curie temperature TC from 365 K for LSMO to 194 K for La067Sr033(Mn08Ni02)O3, which exhibits a cluster glass-like state The oxide is insulating under both zero field and 60 kOe, but application of the magnetic field induces colossal magnetoresistance (CMR) especially at low temperature Far below TC, the compound’s field dependence of resistivity has a very similar shape with that of metallic perovskite manganite at relatively high temperature when the spin fluctuation grows stronger The results indicate that the ferromagnetic superexchange between Ni and Mn, is helpful for the overall ferromagnetic exchange components just overcoming the generic antiferromagnetic exchange components, which leads to the presence of the cluster glass-like state The reduction of the magnetic disorder and the suppression of the spin fluctuation in Mn–O layer by the external magnetic field are suggested to explain the CMR effect in this insulating compound

Colossal electroresistance and current induced switching in ferromagnetic insulating state of La0.82Ca0.18MnO3

Abstract: Colossal electroresistance and current induced resistivity switching have been measured in the ferromagnetic insulating (FMI) state of single crystal manganite La0.82Ca0.18MnO3. The sample has a Curie transition temperature TC = 165 K and the FMI state is realized for temperatures T<100 K. The electroresistance (ER), arising from a strong nonlinear resistivity, attains a large value ( ≈ 100%) in the FMI state. However, this is accompanied by a collapse of the magnetoresistance (MR) to a small value even in magnetic field (H) of 10 T. This demonstrates that the mechanisms that give rise to ER and MR are effectively decoupled.

Structural and magnetotransport properties of the colossal magnetoresistance material Tl{sub 2}Mn{sub 2}O{sub 7}

Abstract: The crystal structure and its variation with temperature of the spin-charge coupled material Tl{sub 2}Mn{sub 2}O{sub 7} pyrochlore is investigated. Structure refinement from the neutron powder-diffraction data reveals that Tl{sub 2}Mn{sub 2}O{sub 7} has nearly stoichiometric composition and is crystallized in the cubic-pyrochlore-type structure with a characteristic Mn-O-Mn bond angle of 133{degree}. There is no structural anomaly associated with the change in magnetotransport properties at 142 K, suggesting weak spin-lattice and charge-lattice correlations. Despite the similarity of magnetotransport properties observed in the perovskite and the pyrochlore colossal magnetoresistance manganese oxides, the double-exchange mechanism, which is usually applied to the perovskite materials, does not seem to explain the behavior in the pyrochlore Tl{sub 2}Mn{sub 2}O{sub 7} compound. A superexchange-type interaction may stabilize the ferromagnetic ordering of Mn spins and cause the metallic conduction at low temperatures in Tl{sub 2}Mn{sub 2}O{sub 7}. {copyright} {ital 1997} {ital The American Physical Society}