Interplay between Charge Order, Magnetism, and Structure in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>La</mml:mi></mml:mrow><mml:mrow><mml:mn>0.875</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>0.125</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>MnO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:

Uhlenbruck, Sven; Teipen, R.; Klingeler, R.; Büchner, B.; Friedt, O.; Hücker, M.; Kierspel, H.; Niemöller, T.; Pinsard, L.; Revcolevschi, A.; Gross, Rudolf

doi:10.1103/physrevlett.82.185

Cited by 125 publications

(77 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is because, in the pure DE picture, an external magnetic field would align the core spins, increase the carrier kinetic energy, and weaken the COO state. As mentioned in 12 , this means that the COO insulating state at low-T is more fully magnetized than the FM-metallic state. In contrast to this, the charge order arising in the N d 0.5 Sr 0.5 M nO 3 samples (which are antiferromagnetically ordered) is weakened by applied fields, suggesting a deep connection between magnetic and orbital degrees of freedom that cannot be accessed within the pure DE model.…”

mentioning

confidence: 80%

Role of orbital degeneracy in double-exchange systems

2001

View full text Add to dashboard Cite

We investigate the role of orbital degeneracy in the double exchange (DE) model. In the JH → ∞ limit, an effective generalized "Hubbard" model incorporating orbital pseudospin degrees of freedom is derived. The model possesses an exact solution in one-and in infinite dimensions. In 1D, the metallic phase off "half-filling" is a Luttinger liquid with pseudospin-charge separation. Using the d = ∞ solution for our effective model, we show how many experimental observations for the welldoped (x ≃ 0.3) three-dimensional manganites La1−xSrxM nO3 can be qualitatively explained by invoking the role of orbital degeneracy in the DE model. PACS numbers: 71.28+d,71.30+h, Colossal magnetoresistance (CMR) materials are presently the focus of much experimental and theoretical attention 1 . These materials are important technologically, owing to the huge decrease of resistivity in modest external magnetic fields (∆R/R ≃ 100000).Early studies of the models for manganites 2 concentrated on the observed link between magnetic and transport properties and studied the "double exchange" (DE) model. This simple model certainly has had a surprising degree of success in explaining the existence of the low-T ferromagnetic metallic (FM) phase in doped La 1−x Sr x M nO 3 with x = 0.3. However, it has come to be subsequently realized that several features of even the high-T phase at x = 0.3, not to mention the existence of a very rich phase diagram 3 , are inexplicable within the framework of the pure DE model. The insulating "normal" state above T F M c at x = 0.33 points to the existence of additional localizing mechanism/s; various candidates considered are (1) a strong coupling of carriers to phonon degrees of freedom 4 , (2) FM short-range order and/or Berry phase effects in the DE model, leading to fluctuations in the hopping and to carrier localization for sufficiently strong spin disorder 5 . The phase diagram of La 1−x Ca x M nO 3 is very rich with regions of ferromagnetic, antiferromagnetic and charge order as a function of x 1 . Optical conductivity measurements and photoemission studies 6 have revealed the transfer of spectral weight over large energy scales, a characteristic of strongly correlated systems. In addition, these studies indicate a small discontinuity in the momentum space occupation fn. n(k), showing up the strongly correlated nature of the FM metallic state. However, the low-T electronic specific heat shows only a modest enhancement of about 2-3 times the bandstructure value 7 . The dc resistivity below T F M c follows ρ(T ) = ρ 0 + AT 2 + BT 9/2 ; the first and the last terms can be reconciled with the DE model 7 , but the AT 2 term with a large A decreasing in an applied field, cannot. Recently, Simpson et al. 8 have carried out a careful study of the optical response of La 0.7 A 0.3 M nO 3 ( A=Ca, Sr ) crystals, which are ferromagnetic metals at low-T . In contrast with earlier measurements yielding optical masses very different from those extracted from specific heat data, these authors have found that the ...

show abstract

mentioning

confidence: 80%

Role of orbital degeneracy in double-exchange systems

2001

View full text Add to dashboard Cite

show abstract

“…While this argument is not strict in the case of the nonmetallic paramagnetic state, it does show that the structural changes that take place at T s have a negligible effect on the overall electronic band structure. In principle, it should also be possible to make a numerical estimate for the effects of the structural correlations on the electrical resistivity [25]. Such estimates require, however, knowledge of the exact structure of the correlated regions and their concentration, which are unknown at this stage.…”

Section: Figmentioning

confidence: 99%

Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites

et al. 2004

View full text Add to dashboard Cite

Neutron scattering measurements on a magnetoresistive manganite La0.75(Ca0.45Sr0.55)0.25MnO3 show that uncorrelated dynamic polaronic lattice distortions are present in both the orthorhombic (O) and rhombohedral (R) paramagnetic phases. The uncorrelated distortions do not exhibit any significant anomaly at the O-to-R transition. Thus, both the paramagnetic phases are inhomogeneous on the nanometer scale, as confirmed further by strong damping of the acoustic phonons and by the anomalous Debye-Waller factors in these phases. In contrast, recent x-ray measurements and our neutron data show that polaronic correlations are present only in the O phase. In optimally doped manganites, the R phase is metallic, while the O paramagnetic state is insulating (or semiconducting). These measurements therefore strongly suggest that the correlated lattice distortions are primarily responsible for the insulating character of the paramagnetic state in magnetoresistive manganites.

show abstract

“…͑2͒ Experimentally, 23 the charge-ordered phase grows larger when an external magnetic field is applied. In our case, we have run a simulation with nonzero magnetic field and, as pointed out in italics in the second next paragraph, our FI phase invades the FM phase and the critical temperature rises.…”

Section: O(2) Symmetrymentioning

confidence: 99%

“…The results point again to no breaking of the O͑2͒ symmetry inside the RP 2 phase. In a series of papers [23][24][25][26] the interplay between FM, AFM, temperature, and an applied magnetic field in the low-doped La 1−x Sr x MnO 3 , mainly at x close to 1 / 8, has been studied. We would like to point out some properties of our FM-FI phase transition ͑point t 2 in this paper͒ which might help to understand phenomena which, in those references, are related to the FM-CO ͑charge ordered͒ phase transition, not fully understood so far.…”

Section: O(2) Symmetrymentioning

confidence: 99%

“…IV D͒ the unusual interplay between ferromagnetism, antiferromagnetism, temperature, and applied magnetic field in low-doped La 1−x Sr x MnO 3 . [23][24][25][26] Let us now address universality. A common wisdom is that the critical properties of a system are given by its dimensionality and the local properties ͑i.e., near the identity element͒ of the coset space G / H, where G is the symmetry group of the Hamiltonian ͑the symmetry of the hightemperature phase͒ and H is the remaining symmetry group of the broken phase ͑low temperature͒.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Phase diagram of the bosonic double-exchange model

Alonso¹,

Cruz²,

Fernández³

et al. 2005

Phys. Rev. B

View full text Add to dashboard Cite

The phase diagram of the simplest approximation to double-exchange systems, the bosonic double-exchange model with antiferromagnetic ͑AFM͒ superexchange coupling, is fully worked out by means of Monte Carlo simulations, large-N expansions, and variational mean-field calculations. We find a rich phase diagram, with no first-order phase transitions. The most surprising finding is the existence of a segmentlike ordered phase at low temperature for intermediate AFM coupling which cannot be detected in neutron-scattering experiments. This is signaled by a maximum ͑a cusp͒ in the specific heat. Below the phase transition, only short-range ordering would be found in neutron scattering. Researchers looking for a quantum critical point in manganites should be wary of this possibility. Finite-size scaling estimates of critical exponents are presented, although large scaling corrections are present in the reachable lattice sizes.

show abstract

Interplay between Charge Order, Magnetism, and Structure inLa0.875Sr0.125MnO3

Cited by 125 publications

References 28 publications

Role of orbital degeneracy in double-exchange systems

Role of orbital degeneracy in double-exchange systems

Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites

Phase diagram of the bosonic double-exchange model

Contact Info

Product

Resources

About