Three-body correlation effects on the spin dynamics of double-exchange ferromagnets
TLDR
In this article, a variational calculation of the spin wave excitation spectrum of double-exchange ferromagnets in different dimensions is presented, which can be used to study the intermediate exchange coupling and electron concentration regime relevant to the manganites.Abstract:
We present a variational calculation of the spin wave excitation spectrum of double-exchange ferromagnets in different dimensions. Our theory recovers the random phase approximation and $1∕S$ expansion results as limiting cases and can be used to study the intermediate exchange coupling and electron concentration regime relevant to the manganites. In particular, we treat exactly the long range three-body correlations between a Fermi sea electron-hole pair and a magnon excitation and show that they strongly affect the spin dynamics. The manifestations of these correlations are many-fold. We demonstrate that they significantly decrease the stability of the ferromagnetic phase and the magnon stiffness. We also show that the ferromagnetic state is unstable against spin wave excitations close to the Brillouin zone boundary. As a result, we find a strong softening of the spin wave dispersion as compared to the Heisenberg ferromagnet with the same stiffness within a range of intermediate concentrations. We discuss the possible relevance of our results to experiments in colossal magnetoresistance ferromagnets.read more
Citations
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Magnons in ferromagnetic metallic manganites.
Jiandi Zhang,Feng Ye,Hao Sha,Pengcheng Dai,Pengcheng Dai,Jaime A. Fernandez-Baca,E. W. Plummer,E. W. Plummer +7 more
TL;DR: 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 is discussed.
Journal ArticleDOI
Femtosecond Control of the Magnetization in Ferromagnetic Semiconductors
J. Chovan,Ilias E. Perakis +1 more
TL;DR: In this article, the authors developed a theory of collective spin dynamics triggered by ultrafast optical excitation of ferromagnetic semiconductors using the density matrix equations of motion in the mean field approximation and including magnetic anisotropy and hole spin dephasing effects.
Journal ArticleDOI
Extensions to the Kondo lattice model to achieve realistic Curie temperatures and appropriate behavior of the resistivity for manganites
Martin Stier,Wolfgang Nolting +1 more
TL;DR: In this paper, the influence of the Jahn-Teller distortion and a direct antiferromagnetic moment coupling as extensions to a two-band Kondo lattice model for the magnetic and electronic properties of manganites was investigated.
Journal ArticleDOI
Magnetization relaxation and collective spin excitations in correlated double-exchange ferromagnets
TL;DR: In this paper, the authors studied spin relaxation and dynamics of collective spin excitations in correlated double-exchange ferromagnets and showed that the collective spin relaxation depends sensitively on three-body correlations between a spin excitation and a Fermi sea electron and hole.
Journal ArticleDOI
Fermionic representation for the ferromagnetic Kondo lattice model: Diagrammatic study of spin-charge coupling effects on magnon excitations
Sudhakar Pandey,Subrat K. Das,Bhaskar Kamble,Saptarshi Ghosh,Dheeraj Kumar Singh,Rajyavardhan Ray,Avinash Singh +6 more
TL;DR: In this article, a purely fermionic representation for the ferromagnetic Kondo lattice model is introduced, which allows conventional diagrammatic tools to be employed to study correlation effects.
References
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Interaction between the d -Shells in the Transition Metals. II. Ferromagnetic Compounds of Manganese with Perovskite Structure
TL;DR: In this paper, it was shown that both electrical conduction and ferromagnetic coupling in these compounds arise from a double exchange process, and a quantitative relation was developed between electrical conductivity and the Ferromagnetic Curie temperature.
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Theory of the role of covalence in the perovskite-type manganites [La,M(II)]MnO3
TL;DR: In this article, the theory of double exchange was applied to perovskite-type manganites and detailed qualitative predictions about the magnetic lattice, the crystallographic lattice and the electrical resistivity were made.
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Colossal Magnetoresistant Materials: The Key Role of Phase Separation
TL;DR: In this paper, a large variety of experiments reviewed in detail here contain results compatible with the theoretical predictions, including phase diagrams of manganite models, the stabilization of the charge/orbital/spin ordered half-doped correlated electronics (CE)-states, the importance of the naively small Heisenberg coupling among localized spins, the setup of accurate mean-field approximations, and the existence of a new temperature scale T∗ where clusters start forming above the Curie temperature, the presence of stripes in the system, and many others.
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Considerations on Double Exchange
TL;DR: In this paper, it was shown that while the states of large total spin have both the highest and lowest energies, their average energy is the same as those of low total spin.
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Giant magnetoresistance of manganese oxides with a layered perovskite structure
TL;DR: In this paper, the authors demonstrate an alternative strategy, in which they synthesize layered variants of the cubic perovskite parent compounds that have a controlled number of MnO2 sheets per unit cell, which is structurally analogous to that employed for the systematic exploration of the high-transition-temperature copper oxide superconductors.