Fermi Surface Nesting and Nanoscale Fluctuating Charge/Orbital Ordering in Colossal Magnetoresistive Oxides

Chuang, Yi‐De; Gromko, A. D.; Dessau, D. S.; Kimura, T.; Tokura, Y.

doi:10.1126/science.1059255

Cited by 183 publications

(158 citation statements)

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“…(6) The systematic measurement of the electronic band structure including the Fermi surfaces, which is crucial to understand the correlation effects on spin dynamics. Though progress in the study of the Fermi surface topology with high-resolution angle-resolved photoelectron spectroscopy (ARPES) has been made in the layered manganites such as La 1.2 Sr 1.8 Mn 2 O 7 [75,76], it is difficult to determine the electronic structure in these three-dimensional manganites because they cannot be cleaved to obtain a reasonably good surface. Surface effects [77,78] due to the surface lattice relaxation, segregation, and/or imperfection would affect the measured electronic structure by using surface sensitive techniques like ARPES.…”

Section: Discussionmentioning

confidence: 99%

Magnons in ferromagnetic metallic manganites

Zhang¹,

Ye²,

Sha³

et al. 2007

J. Phys.: Condens. Matter

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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.

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Section: Discussionmentioning

confidence: 99%

Magnons in ferromagnetic metallic manganites

Zhang¹,

Ye²,

Sha³

et al. 2007

J. Phys.: Condens. Matter

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“…The charging energy associated with nanoscale ferromagnetic grains can be as large as several hundred Kelvins [11] and we require that E c /δ ≫ 1. The typical sample Curie temperature, T s c , of the arrays we consider (and also of doped manganites) is in the range (100 − 200)K, [3,12,13]; thus the temperature interval T s c < T < E c is experimentally accessible. To satisfy the last inequality, the size of a single ferromagnetic grain, a, should be less than the critical size a c = e 2 /(T s c κ).…”

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confidence: 99%

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confidence: 99%

“…Bottom: Schematic behavior of the resistivity, ρ, versus temperature, T , in the different states in the absence (B = 0) and presence (B > 0) of a magnetic field B aligned with the magnetization of the SFM, cf. [3,12].energy E c = e 2 /(κa), where e is the electron charge, κ the sample dielectric constant, and a the granule size, and (ii) the mean energy level spacing δ. The charging energy associated with nanoscale ferromagnetic grains can be as large as several hundred Kelvins [11] and we require that E c /δ ≫ 1.…”

mentioning

confidence: 99%

“…2 for the following set of parameters: ξ 0 /a = 1, T 0 /T s c = 10, and Π 2 = 0.3. In order to describe typical experimental data [12], the normalized distribution function f (θ) was chosen to ensure a sharp drop in the magnetization at a temperature dependent function. For temperatures T s c ≤ T ≪ T 0 it is given by γ T ≃ (ξ 0 /2a) T 0 /T .…”

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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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Electronic states of magnetic materials

Himpsel¹,

Altmann²

2003

Solid‐State Photoemission and Related Methods

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Fermi Surface Nesting and Nanoscale Fluctuating Charge/Orbital Ordering in Colossal Magnetoresistive Oxides

Cited by 183 publications

References 35 publications

Magnons in ferromagnetic metallic manganites

Magnons in ferromagnetic metallic manganites

Electron Transport in Nanogranular Ferromagnets

Electronic states of magnetic materials

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