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Yoshizawa, H.; Kawano, H.; Tomioka, Y.; Tokura, Y.

doi:10.1103/physrevb.52.r13145

Cited by 295 publications

(168 citation statements)

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“…The second feature of this term is that if x < 1/2, it is possible for coexisting magnetism to "cancel" the chemical tendency to incommensurability, and we note that canted magnetism is generally reported [18,24,25] Throughout much of the phase diagram shown in these figures, the order parameters M, ρ and ∇φ are approximately uniform in space, at least for the parameters we have chosen. However, close to the commensurate-incommensurate transition, the phase modulation becomes non uniform, and the phase gradient is built up by periodic discommensurations where the phase advances through 2π/n.…”

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confidence: 99%

“…The second feature of this term is that if x < 1/2, it is possible for coexisting magnetism to "cancel" the chemical tendency to incommensurability, and we note that canted magnetism is generally reported [18,24,25] where the phase advances through 2π/n. In such an inhomogeneous state, magnetism is naturally enhanced at the boundary and the amplitude of the charge modulation suppressed (see Fig.…”

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confidence: 99%

“…Another example of coexistence is given by the underdoped (0.3 < x < 0.5) Pr 1−x Ca x MnO 3 . The ground state is commensurate and charge-modulated [16,17] but the antiferromagnetism is canted [18,24,25], showing a ferromagnetic component coexisting with the commensurate charge modulation.One might propose to explain these phenomena in terms of microscopic theory incorporating the many different couplings and microscopic degrees of freedom, but this is a daunting task that might not be illuminating owing to its complexity. Here we propose a simple and more transparent phenomenological approach to this problem by means of Ginzburg-Landau theory.…”

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Electronically soft phases in manganites

Milward

Calderón

Littlewood

2005

Nature

275

239

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The phenomenon of colossal magnetoresistance in manganites is generally agreed to be a result of competition between crystal phases with different electronic, magnetic, and structural order; a competition which can be strong enough to cause phase separation between metallic ferromagnet and insulating charge modulated states [1,2,3,4,5]. Nevertheless, closer inspection of phase diagrams in many manganites reveals complex phases where the two order parameters of magnetism and charge modulation unexpectedly coexist [6,7].Here we show that such experiments can be naturally explained within a phenomenological Ginzburg-Landau theory.In contrast to models where phase separation originates from disorder [8] or as a strain induced kinetic phenomenon [9], we argue that magnetic and charge modulation coexist in new thermodynamic phases. This leads to a rich diagram of equilibrium phases, qualitatively similar to those seen in experiment. The success of this model argues for a fundamental reinterpretation of the nature of charge modulation in these materials from a localised to a more extended "charge density wave" picture. The same symmetry considerations that favour textured coexistance of charge and magnetic order may apply to many electronic systems with competing phases. The resulting "Electronically soft" phases of matter with incommensurate, inhomogeneous and mixed order may be general phenomena in correlated systems.The manganese perovskites (RE 3+ 1−x AE 2+ x MnO 3 , RE rare earth, AE alkaline earth) provide a laboratory to study the interplay of a variety of magnetic, electronic and structural phases of matter in a strongly correlated electronic system. As in many strongly correlated electronic systems, the basic paradigm for manganite physics is the competition between the delocalising effects of the electron kinetic energy and the localising effects of the Coulomb repulsion, aided by coupling to lattice degrees of freedom. When the kinetic energy is dominant, one finds a metallic ground state with ferromagnetic alignment of the core moments.When the localising effects preponderate, instead we see charge and/or orbitally ordered ground states with substantial local lattice distortions from the near cubic symmetry of the metal, along with insulating behaviour and antiferromagnetism. One may tune between these two phases by many external parameters, especially chemical substitution, but also lattice strain, and magnetic field. The competition between metal and insulator is famously evident in the phenomenon of bulk colossal magnetoresistance, where a magnetic field tunes the conductivity of the material, and even more clearly in the strong tendency toward phase separation and inhomogeneity and regimes of percolative transport.The origin of charge and orbital ordered phases is still the subject of debate. Charge modulation has been traditionally seen as the ordering of Mn 4+ and Mn 3+ ions [10]. More recently, the charge disproportionation of the Mn ions has been argued to be much smaller than one [11,12,13] but sti...

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“…The second feature of this term is that if x < 1/2, it is possible for coexisting magnetism to "cancel" the chemical tendency to incommensurability, and we note that canted magnetism is generally reported [18,24,25] where the phase advances through 2π/n. In such an inhomogeneous state, magnetism is naturally enhanced at the boundary and the amplitude of the charge modulation suppressed (see Fig.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Electronically soft phases in manganites

Milward

Calderón

Littlewood

2005

Nature

275

239

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“…Among various manganites, Pr 1−x Ca x MnO 3 is unique, showing insulating behaviour over the whole composition (x) range due to its narrow bandwidth of 3d conducting e g electrons 7 . The title compound Pr 0.6 Ca 0.4 MnO 3 falls in the range 0.3<x<0.75 where the ground state is charge ordered antiferromagnetic insulator 8,9 . Charge ordering refers to ordering of manganese ions that can be in Mn 3+ or Mn 4+ valence: at low temperatures these ions order into a superstructure forming stripes of Mn 3+ and Mn 4+ ions.…”

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Origin of the colossal dielectric response ofPr0.6Ca0.4MnO3

et al. 2005

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We report the detailed study of dielectric response of Pr0.6Ca0.4MnO3 (PCMO), member of manganite family showing colossal magnetoresistance. Measurements have been performed on four polycrystalline samples and four single crystals, allowing us to compare and extract the essence of dielectric response in the material. High frequency dielectric function is found to be ε0=30, as expected for the perovskite material. Dielectric relaxation is found in frequency window of 20Hz-1MHz at temperatures of 50-200K that yields to colossal low-frequency dielectric function, i.e. static dielectric constant. Static dielectric constant is always colossal, but varies considerably in different samples from ε0=10 3 until 10 5 . The measured data can be simulated very well by blocking (surface barrier) capacitance in series with sample resistance. This indicates that the large dielectric constant in PCMO arises from the Schottky barriers at electrical contacts. Measurements in magnetic field and with d.c. bias support this interpretation. Colossal magnetocapacitance observed in the title compound is thus attributed to extrinsic effects. Weak anomaly at the charge ordering temperature can also be attributed to interplay of sample and contact resistance. We comment our results in the framework of related studies by other groups.

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