Evolution of the Low-Frequency Spin Dynamics in Ferromagnetic Manganites

Fernandez-Baca, J. A.; Dai, Pengcheng; Hwang, H. Y.; Kloc, Ch.; Cheong, S. W.

doi:10.1103/physrevlett.80.4012

Cited by 179 publications

(177 citation statements)

References 22 publications

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“…Meanwhile, it is found [25,26,51,52,56] that the temperature at which the central component appears is related to T C . In Pr 0.63 Sr 0.37 MnO 3 the central component emerges only when T > 0.95T C [25], thus very close to T C .…”

Section: Temperature Dependence and Incoherent Spin Dynamics Near T Cmentioning

confidence: 99%

“…This indicates that there is another effect causing the enhanced magnon damping near the zone boundary rather than the simple magnon-magnon scattering and such effects should be T C dependent. Even in the long-wavelength (low-q) limit, the T dependence of magnons also shows unusual behaviour, which is clearly dependent on T C [19,23,25,26,51,52]. It is found [25,26] that, for low-T C samples, the spin-wave stiffness D(T ) exhibits a power law behaviour as a function of temperature but does not collapse as T → T C , thus challenging the simple theories based on a Heisenberg ferromagnetism and DE model.…”

Section: Temperature Dependence and Incoherent Spin Dynamics Near T Cmentioning

confidence: 99%

“…To determine the evolution of magnon excitations in R 1−x A x MnO 3 as a function of doping, figure 11(a) summarizes the magnon dispersions along the [1, 0, 0] direction for a series of R 1−x A x MnO 3 with x ≈ 0.3 [19,21,25,27,31] while figure 11(b) presents the dispersions along the same direction but for different doping concentrations [21,24,28]. The solid curves in the figure are phenomenological fits to the data using the Heisenberg Hamiltonian equations (3) and (4) with nearest-neighbour (J 1 ) and fourth-nearest-neighbour (J 4 ) exchange coupling.…”

Section: Doping Dependence Of Magnon Excitationsmentioning

confidence: 99%

“…Figure 18 To further characterize the spin dynamics of FM manganites when T → T C several groups have studied the spin diffuse scattering near T C [19,23,25,26,51,52,55,56]. An anomalous and field-dependent central diffusive component which develops above T ∼ 0.8T C for La 0.7 Ca 0.3 MnO 3 [25] and T ∼ 0.9 T C for Nd 0.7 Sr 0.3 MnO 3 [23] and dominates the fluctuation spectrum as T → T C [25,23] has been observed for the low-T C samples, coinciding with the non-collapse behaviour of D(T ). This central component is the result of quasi-elastic spin diffuse scattering.…”

Section: Temperature Dependence and Incoherent Spin Dynamics Near T Cmentioning

confidence: 99%

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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: Temperature Dependence and Incoherent Spin Dynamics Near T Cmentioning

confidence: 99%

Section: Temperature Dependence and Incoherent Spin Dynamics Near T Cmentioning

confidence: 99%

Section: Doping Dependence Of Magnon Excitationsmentioning

confidence: 99%

Section: Temperature Dependence and Incoherent Spin Dynamics Near T Cmentioning

confidence: 99%

See 2 more Smart Citations

Magnons in ferromagnetic metallic manganites

Zhang¹,

Ye²,

Sha³

et al. 2007

J. Phys.: Condens. Matter

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“…11 It is therefore puzzling why isotropic transport and magnetic properties are observed in the FM metallic manganites, 3,12 best exemplified by the isotropic spin waves in La 0.7 Pb 0.3 MnO 3 . 13 In this paper we investigate the microscopic origin of the isotropic magnetic properties of the FM metallic manganites, 12,13 and demonstrate that orbital fluctuations play a prominent role in this phase, stabilizing an isotropic orbital liquid ͑OL͒ phase with disordered orbitals. Thereby we consider ͑i͒ why the FM metallic phase is orbital disordered in a system which seems to have such a strong tendency towards orbital ordering, and ͑ii͒ what the physical meaning is of the increase of the spin-wave stiffness with hole doping x ͑Ref.…”

mentioning

confidence: 99%

Why spin excitations in metallic ferromagnetic manganites are isotropic

Oleś

Feiner

2002

Phys. Rev. B

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We consider the t-J model for doped manganites, and show that double exchange for correlated e g electrons favors in the ferromagnetic metallic phase an orbital liquid ͑i.e., orbital-disordered͒ state. Therefore the spinwave stiffness is isotropic, and increases with hole doping x, providing a direct measure of the kinetic energy ϰx of strongly correlated e g electrons. The superexchange interactions, which stabilize orbital order at low doping, are frustrated in the orbital liquid and only reduce the stiffness constant, leading to a quantitative explanation of the magnon dispersion. DOI: 10.1103/PhysRevB.65.052414 PACS number͑s͒: 75.30.Vn, 71.27.ϩa, 75.30.Ds, 75.30.Et Strong Coulomb interactions in transition-metal oxides are responsible for numerous fascinating phenomena. They suppress charge fluctuations in the Mott-Hubbard insulators, and replace them by superexchange ͑SE͒ interactions. While these interactions are antiferromagnetic ͑AF͒ when they follow just from the Pauli principle for a single orbital, they have a richer structure when degenerate d orbitals are involved, as in cuprates or manganites. It is evident that in such situations the orbital and spin degrees of freedom have to be considered on equal footing, 1 and the SE interactions are highly frustrated even on a cubic lattice. This was recently recognized as the origin of interesting quantum effects both for e g and t 2g electrons. 2 However, in undoped e g systems such frustration is likely removed by the Jahn-Teller ͑JT͒ effect, which leads to a structural phase transition and stabilizes orbital ordering. The best example is undoped LaMnO 3 with A-type AF spin order which coexists with orbital order, 3,4 and can be understood only as a superposition of the cooperative JT effect and the SE. 5 The theoretical understanding of doped manganese oxides La 1Ϫx A x MnO 3 , with AϭSr,Ca,Pb, is among the most challenging current areas of research in condensed-matter physics. Experimental studies have revealed their rich phase diagrams, 3 originating from the competition between charge, spin, and orbital degrees of freedom. Charge fluctuations are thereby partly suppressed by the large Coulomb interaction UӍ5.9 eV ͑Ref. 6͒ between two e g electrons on the same ion. In addition, the Hund's exchange J H Ӎ0.7 eV couples the sϭ1/2 spins of the e g electrons strongly to the S t ϭ3/2 core spins of the t 2g electrons, resulting in large Sϭ2 spins of Mn 3ϩ ions. When LaMnO 3 is doped, holes that are created in e g orbitals can move but only when all spins are parallel, as explained by the double-exchange ͑DE͒ mechanism, 7 thus leading to a ferromagnetic ͑FM͒ state. When the orbital degeneracy is ignored, as in the original DE theory, isotropic magnon excitations are obtained. 8 However, when the orbital degrees of freedom are taken into account, one finds that the kinetic energy is lowered when orbital order occurs and the system becomes effectively lower dimensional. 9-11 Such states have broken cubic symmetry, and thus anisotropic magnetic excitations. 11...

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Magnons in the Ferromagnetic Kondo-Lattice Model

Vogt

Santos

Nolting

2001

phys. stat. sol. (b)

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The magnetic properties of the ferromagnetic Kondo-lattice model (FKLM) are investigated. Starting from an analysis of the magnon spectrum in the spin-wave regime, we examine the ferromagnetic stability as a function of the occupation of the conduction band n and the strength J of the coupling between the localised moments and the conduction electrons. From the properties of the spin-wave stiffness D the ferromagnetic phase at zero temperature is derived. Using an approximate formula the critical temperature T c is calculated as a function of J and n.

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Evolution of the Low-Frequency Spin Dynamics in Ferromagnetic Manganites

Cited by 179 publications

References 22 publications

Magnons in ferromagnetic metallic manganites

Magnons in ferromagnetic metallic manganites

Why spin excitations in metallic ferromagnetic manganites are isotropic

Magnons in the Ferromagnetic Kondo-Lattice Model

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