Nanoscale Phase Separation and Colossal Magnetoresistance

Dagotto, Elbio

doi:10.1007/978-3-662-05244-0

Cited by 954 publications

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“…The total refined moment of the system was 3.689 µ B , as shown in Table II, smaller than our crude Curie-Weiss fit but still robust. This spin structure is different from the canonical A-type, E-type, CE-type, C-type, G-type, and spiral-type antiferromagnetic phases observed in manganites before (using the canonical notation 39,40 ). Although the single crystal neu- tron data enables us to resolve the antiferromagnetic spin structure, the broadness of the magnetic Bragg peaks strongly suggests that this antiferromagnetic ordering either has short range characteristics or it has a clustered nature, as opposed to a true long range magnetic ordering.…”

Section: Resultscontrasting

confidence: 81%

“…[39][40][41] In the past decade, this model Hamiltonian has been widely used to investigate a plethora of magnetic phases and their associated physical characteristics, such as colossal magnetoresistance and multiferroicity, in perovskite manganites. 39,40 The clear success of the previous efforts in this context allows us to investigate with confidence the possibility of new phases in previously unexplored regions of the phase diagrams via the double exchange model. More explicitly, the model Hamiltonian used here reads as:…”

Section: Discussionmentioning

confidence: 99%

“…39,40 The three nearestneighbor (NN) hopping directions are denoted by r. Two e g orbitals (a: x 2 − y 2 and b: 3z 2 − r 2 ) are involved in the double-exchange process for manganites, with the…”

Section: Discussionmentioning

confidence: 99%

“…This hopping can be roughly estimated to be 0.5 eV. 39,40 The second term of the Hamiltonian is the antiferromagnetic superexchange interaction between the NN t 2g spins.…”

Section: Discussionmentioning

confidence: 99%

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Canted magnetic ground state of quarter-doped manganitesR_0.75Ca_0.25MnO₃(R = Y, Tb, Dy, Ho, and Er)

Sinclair

Cao

Garlea

et al. 2016

J. Phys.: Condens. Matter

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Polycrystalline samples of the quarter-doped manganites R0.75Ca0.25MnO3 (R = Y, Tb, Dy, Ho, and Er) were studied by X-ray diffraction and AC/DC susceptibility measurements. All five samples are orthorhombic and exhibit similar magnetic properties: enhanced ferromagnetism below T1 (∼ 80 K) and a spin glass (SG) state below TSG (∼ 30 K). With increasing R 3+ ionic size, both T1 and TSG generally increase. The single crystal neutron diffraction results on Tb0.75Ca0.25MnO3 revealed that the SG state is mainly composed of a short-range ordered version of a novel canted (i.e. noncollinear) antiferromagnetic spin state. Furthermore, calculations based on the double exchange model for quarter-doped manganites reveal that this new magnetic phase provides a transition state between the ferromagnetic state and the theoretically predicted spin-orthogonal stripe phase.

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Section: Resultscontrasting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…This hopping can be roughly estimated to be 0.5 eV. 39,40 The second term of the Hamiltonian is the antiferromagnetic superexchange interaction between the NN t 2g spins.…”

Section: Discussionmentioning

confidence: 99%

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Canted magnetic ground state of quarter-doped manganitesR_0.75Ca_0.25MnO₃(R = Y, Tb, Dy, Ho, and Er)

Sinclair

Cao

Garlea

et al. 2016

J. Phys.: Condens. Matter

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“…Many interesting materials ranging from magnetorestrictive manganite films [1] and field-effect transistors [2,3], to unconventional low dimensional superconductors [4], find themselves close to the metal-insulator transition. In this regime, competition between several distinct ground states [4] produces unusual behavior, displaying striking similarities in a number of different systems.…”

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confidence: 99%

Self-generated electronic heterogeneity and quantum glassiness in the high-temperature superconductors

Panagopoulos

Dobrosavljević

2005

Phys. Rev. B

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We present a systematic study of the spin and charge dynamics of copper oxide superconductors as a function of carrier concentration x. Our results portray a coherent physical picture, which reveals a quantum critical point at optimum doping (x = xopt), and the formation of an inhomogeneous glassy state at x < xopt. This mechanism is argued to arise as an intrinsic property of doped Mott insulators, and therefore to be largely independent of material quality and level of disorder.Many interesting materials ranging from magnetorestrictive manganite films [1] and field-effect transistors [2,3], to unconventional low dimensional superconductors [4], find themselves close to the metal-insulator transition. In this regime, competition between several distinct ground states [4] produces unusual behavior, displaying striking similarities in a number of different systems. Electronic heterogeneity [1,5] emerges, giving rise to "mesoscopic" coexistence of different ordered phases. Typically, a large number of possible configurations of these local regions have comparable energies, resulting in slow relaxation, aging, and other signatures of glassy systems. Because the stability of such ordering is controlled by doping-dependent quantum fluctuations [6,7] introduced by itinerant carriers, these systems can be regarded as prototypical quantum glasses -a new paradigm of strongly correlated matter.In this Letter we report the emergence and evolution of dynamical heterogeneity and glassy behavior across the phase diagram of the high-transition-temperature (T c ) superconductors (HTS). Based on data of the spin and charge dynamics, we draw a phase diagram (Fig. 1) and propose that self generated glassiness [5] may be a key feature necessary to understand many of the unconventional properties of both the superconducting and the normal state.Glassiness in the pseudo-gap phase. In the archetypal HTS, La 2−x Sr x CuO 4 (LSCO) the parent 2D antiferromagnetic insulator (AFI) La 2 CuO 4 displays a sharp peak in the magnetic susceptibility at the Neel temperature T N = 300K. T N decreases with hole-doping and the transition width broadens (Fig. 2 -upper panel). Concurrently, there is systematic experimental evidence from various techniques and on several HTS that a second freezing transition (T F ) emerges at lower temperatures with the first added holes (Fig. 2) [8,9,10,11,12,13]. At x > 0.02, T N = 0 but the short range order persists [14]: the low-field susceptibility displays a cusp at low temperatures and a thermal hysteresis below, characteristic of a spin glass transition (T g ) (Fig. 2 -upper panel). At T < T g the material displays memory effects like "traditional" spin glasses and is described by an Edwards-Anderson order parameter [15]. Interestingly, it is at this doping range that a pseudogap phase develops [4,16].

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Orbital Physics in Transition Metal Oxides: Magnetism and Optics

Horsch¹

2007

Handbook of Magnetism and Advanced Magnetic Materials

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Orbital degeneracy and strong correlations in transition‐metal oxides generate spins and orbitals as low‐energy degrees of freedom. Their interplay with both real‐charge motion and virtual‐charge excitations lead to a fascinating richness of spin–charge–orbital‐ordered phases in transition‐metal oxides, to striking phenomena like the colossal magnetoresistance in manganites, the switching of charge‐ordered phases into metallic phases by applied magnetic field, and many other fascinating effects. Central topics of this review are the spin‐orbital superexchange models which provide a concise description of spin and orbital order, effective spin interactions, spin waves, and orbiton excitations in doped and undoped Mott insulators. Particular emphasis is put on recent developments of spin‐orbital superexchange models, the relation of magnetism and optical spectral weights and their temperature dependence, t 2g systems with strong composite spin‐orbital fluctuations, the concepts of orbital liquid, orbital polarons, and the colossal magnetoresistance.

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Nanoscale Phase Separation and Colossal Magnetoresistance

Cited by 954 publications

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Canted magnetic ground state of quarter-doped manganitesR_0.75Ca_0.25MnO₃(R = Y, Tb, Dy, Ho, and Er)

Canted magnetic ground state of quarter-doped manganitesR_0.75Ca_0.25MnO₃(R = Y, Tb, Dy, Ho, and Er)

Self-generated electronic heterogeneity and quantum glassiness in the high-temperature superconductors

Orbital Physics in Transition Metal Oxides: Magnetism and Optics

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Nanoscale Phase Separation and Colossal Magnetoresistance

Cited by 954 publications

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Canted magnetic ground state of quarter-doped manganitesR0.75Ca0.25MnO3(R = Y, Tb, Dy, Ho, and Er)

Canted magnetic ground state of quarter-doped manganitesR0.75Ca0.25MnO3(R = Y, Tb, Dy, Ho, and Er)

Self-generated electronic heterogeneity and quantum glassiness in the high-temperature superconductors

Orbital Physics in Transition Metal Oxides: Magnetism and Optics

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Product

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Canted magnetic ground state of quarter-doped manganitesR_0.75Ca_0.25MnO₃(R = Y, Tb, Dy, Ho, and Er)

Canted magnetic ground state of quarter-doped manganitesR_0.75Ca_0.25MnO₃(R = Y, Tb, Dy, Ho, and Er)