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Franck, J. P.; Isaac, I.; Chen, Weimin; Chrzanowski, J.; Irwin, J. C.

doi:10.1103/physrevb.58.5189

Cited by 66 publications

(69 citation statements)

References 35 publications

(28 reference statements)

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“…2 and Eqs. (11), (12) suggest that the diagrams Σ 1b and Σ 1c can be absorbed in a γ-dependent λ c as follows:…”

Section: Discussionmentioning

confidence: 99%

“…Recent observations in several classes of "strongly correlated" materials (high-temperature superconductors, "colossal magnetoresistance" manganites, and alkalimetal doped C 60 ) of large isotope effects on electronic properties, including electron effective mass 4-8 and superconducting, 4-9 magnetic, [10][11][12][13] and charge ordering [14][15][16][17] transition temperatures pose a fundamental challenge to this understanding and call for a theory that goes beyond ME. Some authors 6,7,10,12 have attempted to relate their experimental data to formulas derived for the case of a "polaron": a single electron interacting with lattice deformation.…”

Section: Introductionmentioning

confidence: 99%

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Dynamical mean-field theory of electron-phonon interactions in correlated systems: Application to isotope effects on electronic properties

Deppeler

Millis

2002

Phys. Rev. B

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We use a recently developed formalism (combining an adiabatic expansion and dynamical meanfield theory) to obtain expressions for isotope effects on electronic properties in correlated systems. As an example we calculate the isotope effect on electron effective mass for the Holstein model as a function of electron-phonon interaction strength and doping. Our systematic expansion generates diagrams neglected in previous studies, which turn out to give the dominant contributions. The isotope effect is small unless the system is near a lattice instability. We compare this to experiment. 71.38.Cn, 71.27.+a

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“…2 and Eqs. (11), (12) suggest that the diagrams Σ 1b and Σ 1c can be absorbed in a γ-dependent λ c as follows:…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamical mean-field theory of electron-phonon interactions in correlated systems: Application to isotope effects on electronic properties

Deppeler

Millis

2002

Phys. Rev. B

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“…The region that looks most affected by oxygen isotope substitution at these temperatures is between 20 and 40 meV where the scattering intensity near 30 meV is lower for the 18 O sample than the 16 O sample. Raman measurements by Franck et al 51 near 0 K showed that the oxygen modes at 28 meV and 53 meV are shifted downward by 1 meV and 2.6 meV for the 18 O sample. At low temperatures (inset) there does seem to be a difference in the spectra at 68 meV where the 16 O peak may be slightly higher and more clearly defined.…”

mentioning

confidence: 99%

“…12 the observed oxygen isotope effect has been partially attributed to different oxygen stoichiometry. 51 For the present samples the high resolution powder diffraction measurements could be used to establish that the oxygen contents for both samples were identical within experimental uncertainties, and thus there can be no significant variation in T C due to the total oxygen content. The lattice parameters, average atomic positions and occupancies were identical as well.…”

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confidence: 99%

First-order nature of the ferromagnetic phase transition in(La‐Ca)MnO3near optimal doping

et al. 2004

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Neutron scattering has been used to study the nature of the ferromagnetic transition in single crystals of La0.7Ca0.3MnO3 and La0.8Ca0.2MnO3, and polycrystalline samples of La0.67Ca0.33MnO3 and La 5/8 Ca 3/8 MnO3 where the naturally occurring 16 O can be replaced with the 18 O isotope. Small angle neutron scattering on the x = 0.3 single crystal reveals a discontinuous change in the scattering at the Curie temperature for wave vectors below ≈0.065Å −1 . Strong relaxation effects are observed for this domain scattering, for the magnetic order parameter, and for the quasielastic scattering, demonstrating that the transition is not continuous in nature, in good agreement with the temperature dependence of the central component of the magnetic fluctuation spectrum, the polaron correlations, and the spin stiffness reported previously. This behavior contrasts with the continuous behavior observed for the x = 0.2 crystal, which is well away from optimal doping. There is a large oxygen isotope effect observed for the TC in the polycrystalline samples, and the Curie temperature is decreased by 7 K by substituting 50%18 O in the x = 0.33 sample. For the optimally doped x = 3/8 sample we observed TC( 16 O) = 266.5 K and TC( 18 O) = 261.5 K at 90% 18 O substitution. Although TC is decreased by 5 K for the x = 3/8 sample the temperature dependence of the spinwave stiffness is found to be identical for the two samples. These results indicate that TC is not solely determined by the magnetic subsystem, but instead the ferromagnetic phase is truncated by the formation of polarons which cause an abrupt transition to the paramagnetic, insulating state. Application of uniaxial stress in the x = 0.3 single crystal sharply enhances the polaron scattering at room temperature. Measurements of the phonon density-of-states show only modest differences above and below TC and between the two different isotopic samples. 75.47.Gk, 75.47.Lx, 75.30.Ds, 63.20.Dj

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“…They are La 1−x Ca x MnO 3 [18,19], Pr 1−x Ca x MnO 3 [20], RuSr 2 GdCu 2 [21], ZrZn 2 [22] and SrRuO 3 [23]. First three compounds La 1−x Ca x MnO 3 , Pr 1−x Ca x MnO 3 and RuSr 2 GdCu 2 show that T c decreases upon the isotope substitution 16 O→ 18 O.…”

Section: Introductionmentioning

confidence: 99%

Isotope shift of the ferromagnetic transition temperature in itinerant ferromagnets

2017

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We present a theory of the isotope effect of the Curie temperature T c in itinerant ferromagnets. The isotope effect in ferromagnets occurs via the electron-phonon vertex correction and the effective attractive interaction mediated by the electron-phonon interaction. The decrease of the Debye frequency increases the relative strength of the Coulomb interaction, which results in a positive isotope shift of T c when the mass M of an atom increases. Following this picture, we evaluate the isotope effect of T c by using the Stoner theory and a spin-fluctuation theory. When T c is large enough as large as or more than 100K, the isotope effect on T c can be measurable. Recently, precise measurements on the oxygen isotope effect on T c have been performed for itinerant ferromagnet SrRuO 3 with T c ∼ 160K. A clear isotope effect has been observed with the positive shift of T c ∼ 1K by isotope substitution ( 16 O → 18 O). This experimental result is consistent with our theory.

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Oxygen-isotope effect of the paramagnetic-insulating to ferromagnetic-metallic transition inLa1−xCax

Cited by 66 publications

References 35 publications

Dynamical mean-field theory of electron-phonon interactions in correlated systems: Application to isotope effects on electronic properties

Dynamical mean-field theory of electron-phonon interactions in correlated systems: Application to isotope effects on electronic properties

First-order nature of the ferromagnetic phase transition in(La‐Ca)MnO3near optimal doping

Isotope shift of the ferromagnetic transition temperature in itinerant ferromagnets

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