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Journal ArticleDOI

Dynamic Jahn-Teller Effect and Colossal Magnetoresistance in La 1-x Sr x MnO 3

01 Jul 1996-Physical Review Letters (American Physical Society)-Vol. 77, Iss: 1, pp 175-178
TL;DR: A model which incorporates the physics of dynamic Jahn-Teller and double-exchange effects is presented and solved via a dynamical mean field approximation to reproduce the behavior of the resistivity and magnetic transition temperature observed in Sr_x MnO_3.
Abstract: A model for the doped rare-earth manganites such as ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ incorporating the physics of dynamic Jahn-Teller and double-exchange effects is presented and solved via a dynamical mean field approximation. The interplay of these two effects as the electron phonon coupling is varied reproduces the observed behavior of the resistivity and magnetic transition temperature.
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Journal ArticleDOI
TL;DR: In this paper, a large variety of experiments reviewed in detail here contain results compatible with the theoretical predictions, including phase diagrams of manganite models, the stabilization of the charge/orbital/spin ordered half-doped correlated electronics (CE)-states, the importance of the naively small Heisenberg coupling among localized spins, the setup of accurate mean-field approximations, and the existence of a new temperature scale T∗ where clusters start forming above the Curie temperature, the presence of stripes in the system, and many others.

2,927 citations


Cites background or methods or result from "Dynamic Jahn-Teller Effect and Colo..."

  • ...The results of Millis et al. (1996) for ¹ and the resistivity at a "xed density n"1 when plotted as a function of had formal similarities with experimental results (which are produced as a function of density)....

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  • ...Millis et al. (1996) argued that the ratio "E /t dominates the physics of the problem....

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  • ...Millis et al. (1996b) argued that a dynamical JT e!ect may persist at higher hole densities, without leading to long-range order but producing important #uctuations that localize electrons by splitting the degenerate e levels at a given MnO octahedron....

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  • ...Jahn}Teller phonons and polarons Millis et al. (1996) (see alsoMillis et al., 1996a; Millis, 1998) argued that the physics of manganites is dominated by the interplay between a strong electron}phonon coupling and the large Hund coupling e!ect that optimizes the electronic kinetic energy by the…...

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  • ...Actually, Millis et al. (1996) concluded that is between 1.3 and 1.5....

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Journal ArticleDOI
10 Jun 1999-Nature
TL;DR: In this article, it was shown that the magnetoresistive response increases dramatically when the Curie temperature (T C) is reduced, and that the massive magnetoresistance in low-T C systems can be explained by percolative transport through the ferromagnetic domains; this depends sensitively on the relative spin orientation of adjacent magnetoric domains which can be controlled by applied magnetic fields.
Abstract: Colossal magnetoresistance1—an unusually large change of resistivity observed in certain materials following application of magnetic field—has been extensively researched in ferromagnetic perovskite manganites. But it remains unclear why the magnetoresistive response increases dramatically when the Curie temperature (T C) is reduced. In these materials, T C varies sensitively with changing chemical pressure; this can be achieved by introducing trivalent rare-earth ions of differing size into the perovskite structure2,3,4, without affecting the valency of the Mn ions. The chemical pressure modifies local structural parameters such as the Mn–O bond distance and Mn–O–Mn bond angle, which directly influence the case of electron hopping between Mn ions (that is, the electronic bandwidth). But these effects cannot satisfactorily explain the dependence of magnetoresistance on T C. Here we demonstrate, using electron microscopy data, that the prototypical (La,Pr,Ca)MnO3 system is electronically phase-separated into a sub-micrometre-scale mixture of insulating regions (with a particular type of charge-ordering) and metallic, ferromagnetic domains. We find that the colossal magnetoresistive effect in low-T C systems can be explained by percolative transport through the ferromagnetic domains; this depends sensitively on the relative spin orientation of adjacent ferromagnetic domains which can be controlled by applied magnetic fields.

1,417 citations

Journal ArticleDOI
01 Sep 1997
TL;DR: In this paper, the authors review recent experimental work falling under the broad classification of colossal magnetoresistance (CMR), which is magnetoreduction associated with a ferromagnetic-toparamagnetic phase transition.
Abstract: We review recent experimental work falling under the broad classification of colossal magnetoresistance (CMR), which is magnetoresistance associated with a ferromagnetic-toparamagnetic phase transition. The prototypical CMR compound is derived from the parent compound, perovskite LaMnO 3. When hole doped at a concentration of 20–40% holes/Mn ion, for instance by Ca or Sr substitution for La, the material displays a transition from a high-temperature paramagnetic insulator to a low-temperature ferromagnetic metal. Near the phase transition temperature, which can exceed room temperature in some compositions, large magnetoresistance is observed and its possible application in magnetic recording has revived interest in these materials. In addition, unusual magneto-elastic effects and charge ordering have focused attention on strong electron–phonon coupling. This coupling, which is a type of dynamic extended-system version of the Jahn–Teller effect, in conjunction with the double-exchange interaction, is also viewed as essential for a microscopic description of CMR in the manganite perovskites. Large magnetoresistance is also seen in other systems, namely Tl 2Mn2O7 and some Cr chalcogenide spinels, compounds which differ greatly from the manganite perovskites. We describe the relevant points of contrast between the various CMR materials.

1,336 citations

Journal ArticleDOI
23 Apr 1998-Nature
TL;DR: In this article, a spin-resolved photoemission measurements of a ferromagnetic manganese perovskite, La 0.7Sr0.3MnO3, was reported.
Abstract: Half-metallic materials are characterized by the coexistence of metallic behaviour for one electron spin and insulating behaviour for the other. Thus, the electronic density of states is completely spin polarized at the Fermi level, and the conductivity is dominated by these metallic single-spin charge carriers. This exotic physical property could have a significant effect on technological applications related to magnetism and spin electronics. Some ferromagnetic systems, such as Heusler compounds1 and chromium dioxide2, have been predicted theoretically to be half-metallic. However, a half-metallic system has not been demonstrated directly and the predictions are still in doubt3,4. Here we report spin-resolved photoemission measurements of a ferromagnetic manganese perovskite, La0.7Sr0.3MnO3, which directly manifest the half-metallic nature well below the Curie temperature. For the majority spin, the photoemission spectrum clearly shows a metallic Fermi cut-off, whereas for the minority spin, it shows an insulating gap with disappearance of spectral weight at ∼0.6 eV binding energy.

1,151 citations

Journal ArticleDOI
26 Mar 1999-Science
TL;DR: Experimental data reviewed here by applying several techniques for manganites and other materials are consistent with a transition between the antiferromagnetic insulator state of the hole-undoped limit and the ferromagnetic metal at finite hole density through a mixed-phase process.
Abstract: Recent computational studies of models for manganese oxides have revealed a rich phase diagram, which was not anticipated in early calculations in this context performed in the 1950s and 1960s. In particular, the transition between the antiferromagnetic insulator state of the hole-undoped limit and the ferromagnetic metal at finite hole density was found to occur through a mixed-phase process. When extended Coulomb interactions are included, a microscopically charged inhomogeneous state should be stabilized. These phase separation tendencies, also present at low electronic densities, influence the properties of the ferromagnetic region by increasing charge fluctuations. Experimental data reviewed here by applying several techniques for manganites and other materials are consistent with this scenario. Similarities with results previously discussed in the context of cuprates are clear from this analysis, although the phase segregation tendencies in manganites appear stronger.

1,026 citations