Phase Separation in Electronic Models for Manganites

Yunoki, Seiji; Hu, Jun; Malvezzi, André Luiz; Moreo, Adriana; Furukawa, Nobuo; Dagotto, Elbio

doi:10.1103/physrevlett.80.845

Cited by 515 publications

(599 citation statements)

References 33 publications

(37 reference statements)

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“…It will be argued later that motivations (1), (2), and (3) are actually interconnected. The rich phase diagram (2) causes phase competition and concomitant inhomogeneities (3), which themselves induce CMR (1).…”

Section: Inhomogeneities In Manganites and Other Com-poundsmentioning

confidence: 99%

“…Several theoretical studies have also produced considerable evidence for the intrinsic tendency of electrons in these materials to induce competing states that are expected to separate microscopically. Some of these theoretical studies were reported even before the inhomogeneous states were clearly identified in experiments, highlighting the remarkable cross-fertilization between theory and experiments that exists in this area of investigation [2,3]. Reviews on this topic, in the manganite context, are already published [4,5].…”

Section: Introductionmentioning

confidence: 99%

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Nanoscale phase separation in colossal magnetoresistance materials: lessons for the cuprates?

Dagotto

Burgy

Moreo

2003

Solid State Communications

107

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A recent vast experimental and theoretical effort in manganites has shown that the colossal magnetoresistance effect can be understood based on the competition of charge-ordered and ferromagnetic phases. The general aspects of the theoretical description appear to be valid for any compound with intrinsic phase competition. In high temperature superconductors, recent experiments have shown the existence of intrinsic inhomogeneities in many materials, revealing a phenomenology quite similar to that of manganese oxides. Here, the results for manganites are briefly reviewed with emphasis on the general aspects. In addition, theoretical speculations are formulated in the context of Cu-oxides by mere analogy with manganites. This includes a tentative explanation of the spin-glass regime as a mixture of antiferromagnetic and superconducting islands, the rationalization of the pseudogap temperature T * as a Griffiths temperature where clusters start forming upon cooling, the prediction of "colossal" effects in cuprates, and the observation that quenched disorder may be far more relevant in Cu-oxides than previously anticipated.

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Section: Inhomogeneities In Manganites and Other Com-poundsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nanoscale phase separation in colossal magnetoresistance materials: lessons for the cuprates?

Dagotto

Burgy

Moreo

2003

Solid State Communications

107

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“…At the same time the model of weakly coupled nanoscale ferromagnetic grains proved to be useful for understanding the transport properties of doped manganite systems [5,6] that have intrinsic inhomogeneities. Recent studies showed that above the Curie temperature these materials possess a nanoscale ferromagnetic cluster structure which to a large extend controls transport in these systems [7,8,9,10]. This defines an urgent quest for understanding and quantitative description of electronic transport in ferromagnetic nanodomain materials based on the model of nanogranular ferromagnets.…”

mentioning

confidence: 99%

Electron Transport in Nanogranular Ferromagnets

2007

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We study electronic transport properties of ferromagnetic nanoparticle arrays and nanodomain materials near the Curie temperature in the limit of weak coupling between the grains. We calculate the conductivity in the Ohmic and non-Ohmic regimes and estimate the magnetoresistance jump in the resistivity at the transition temperature. The results are applicable for many emerging materials, including artificially self-assembled nanoparticle arrays and a certain class of manganites, where localization effects within the clusters can be neglected.PACS numbers: 73.43.Qt Arrays of ferromagnetic nanoparticles are becoming one of the mainstreams of current mesoscopic physics [1,2,3,4]. Not only ferromagnetic granules promise to serve as logical units and memory storage elements meeting elevated needs of emerging technologies, but also offer an exemplary model system for investigation of disordered magnets. At the same time the model of weakly coupled nanoscale ferromagnetic grains proved to be useful for understanding the transport properties of doped manganite systems [5,6] that have intrinsic inhomogeneities. Recent studies showed that above the Curie temperature these materials possess a nanoscale ferromagnetic cluster structure which to a large extend controls transport in these systems [7,8,9,10]. This defines an urgent quest for understanding and quantitative description of electronic transport in ferromagnetic nanodomain materials based on the model of nanogranular ferromagnets.In this paper we investigate electronic transport properties of arrays of ferromagnetic grains [11] near the ferromagnetic-paramagnetic transition, see Fig. 1. At low temperatures, T < T s c , the sample is in a so called superferromagnetic (SFM) state, see Fig. 1, set up by dipole-dipole interactions. Near the macroscopic Curie temperature, T s c , thermal fluctuations destroy the macroscopic ferromagnetic order. At intermediate temperatures T s c < T < T g c , where T g c is the Curie temperature of a single grain, the system is in a superparamagnetic (SPM) state where each grain has its own magnetic moment while the global ferromagnetic order is absent. At even higher temperatures, T > T g c , the ferromagnetic state within each grain is destroyed and the complete sample is in a paramagnetic state. We consider the model of weakly interacting grains in which the sample Curie temperature is much smaller than the Curie temperature of a single grain, T s c ≪ T g c . We first focus on the SPM state, and discuss a d−dimensional array (d = 3, 2) of ferromagnetic grains taking into account Coulomb interactions between electrons. Granularity introduces additional energy parameters apart from the two Curie temperatures, T g c and T s c : each nanoscale cluster is characterized by (i) the charging c , where T s c is the macroscopic Curie temperature of the system, the ferromagnetic grains (superspins) form a superferromagnet (SFM); for T s c < T < T g c , where T g c is the Curie temperature for a single grain, the system is in a superparamagne...

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“…A similar phase separation has also been reported for the Kondo lattice model with ferromagnetic Hund's coupling, in which near half filling, there is a region of the phase diagram in which the ferromagnetic phase gives place to a phase-separated regime with hole-undoped antiferromagnetic and hole-rich ferromagnetic regions. 30 Thirdly, the appearance of another ferromagnetic region close to n = 1.75 has been suggested in Ref. 31; this phase would be analogous to the one obtained for the Kondo lattice model in Ref.…”

Section: Intermediate Fillingsmentioning

confidence: 87%

Incommensurate spin-density-wave and metal-insulator transition in the one-dimensional periodic Anderson model

et al. 2011

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We have used the density-matrix renormalization group method to study the ground-state properties of the symmetric periodic Anderson model in one dimension. We have considered lattices with up to N s = 50 sites, and electron densities ranging from quarter to half filling. Through the calculation of energies, correlation functions, and their structure factors, together with careful extrapolations (toward N s → ∞), we were able to map out a phase diagram U vs n, where U is the electronic repulsion on f orbitals, and n is the electronic density, for a fixed value of the hybridization. At quarter filling, n = 1, our data is consistent with a transition at U c 1 2, between a paramagnetic (PM) metal and a spin-density-wave (SDW) insulator; overall, the region U 2 corresponds to a PM metal for all n < 2. For 1 < n 1.5 a ferromagnetic phase is present within a range of U , while for 1.5 n < 2, we find an incommensurate SDW phase; above a certain U c (n), the system displays a Ruderman-Kittel-Kasuya-Yosida behavior, in which the magnetic wave vector is determined by the occupation of the conduction band. At half filling, the system is an insulating spin liquid, but with a crossover between weak and strong magnetic correlations.

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Phase Separation in Electronic Models for Manganites

Cited by 515 publications

References 33 publications

Nanoscale phase separation in colossal magnetoresistance materials: lessons for the cuprates?

Nanoscale phase separation in colossal magnetoresistance materials: lessons for the cuprates?

Electron Transport in Nanogranular Ferromagnets

Incommensurate spin-density-wave and metal-insulator transition in the one-dimensional periodic Anderson model

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