Zener Polaron Ordering in Half-Doped Manganites

Daoud‐Aladine, A.; Rodrı́guez-Carvajal, J.; Pinsard-Gaudart, L.; Fernández‐Díaz, M. T.; Revcolevschi, A.

doi:10.1103/physrevlett.89.097205

Cited by 287 publications

(156 citation statements)

References 23 publications

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“…Labels on ions refer to Tables I to III. two states is in charge on O ions rather than Mn ions and so CO may be associated with O ions rather than Mn ions. Furthermore, we find that the lowest energy structure for either CO pattern has a different space group from those proposed for the CB [2] or ZP [14] structures. The structure that we find has modulations of Mn and O ion positions about ideal perovskite positions which are parallel to ab planes and transverse to the b axis and are similar to those observed in layered [4,5]and simple doped manganites [1,2,3,6,7,8].…”

Section: +mentioning

confidence: 55%

“…Initial atomic configurations were taken from Table II in Ref. [2] (P 112 1 /m symmetry) or were generated by hand. As noted by Daoud-Aladine and coworkers [14], the isotropy subgroups of the parent high temperature Pbnm phase that have a doubled unit cell along the b axis are: P 11m, P 2 1 nm, P 112 1 /m, P 112 1 /b, P 2 1 nb and P 11b. The relevant isotropy subgroups for ZP CO are P 2 1 nm and P 11m and for CB CO they are P 112 1 /m [2] and P 11m.…”

Section: +mentioning

confidence: 77%

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Competing crystal structures inLa0.5Ca0.5MnO3: Conventional charge order versus Zener polarons

Patterson

2005

Phys. Rev. B

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Equilibrium crystal structures for La0.5Ca0.5MnO3 have been calculated using hybrid exact exchange and density functional methods. Two distinct ground states with either conventional checkerboard charge ordering or Zener polaron formation are found depending on the proportion of exact exchange used. The checkerboard state has mixed d x 2 −y 2 , d 3x 2 −r 2 and d 3y 2 −r 2 orbital ordering and CE-type magnetic order while the Zener polaron state has d 3x 2 −r 2 and d 3y 2 −r 2 ordering and A-type magnetic order.

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Section: +mentioning

confidence: 55%

Section: +mentioning

confidence: 77%

Competing crystal structures inLa0.5Ca0.5MnO3: Conventional charge order versus Zener polarons

Patterson

2005

Phys. Rev. B

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“…As t is lowered further, this phase is followed by the appearance of Type-CE AF order in which the ferromagnetic (001) planes break up into ferromagnetic zig-zag chains coupled antiparallel to one another; the chains appear to contain two-manganese Zener polarons in which the average manganese valence is 3.5+. 27,33 The charge-ordered Type-CE AF phase at t<t c contains distinguishable Mn(IV) and Mn(III) ions. At t=t c , a unique ferromagnetic phase suppresses both CO and OO down to lowest temperatures.…”

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confidence: 99%

Phase competition inL0.5A0.5MnO3perovskites

et al. 2002

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Single crystals of the systems Pr 0.5 (Ca 1-x Sr x ) 0.5 MnO 3 , (Pr 1-y Y y ) 0.5 (Ca 1-x Sr x ) 0.5 MnO 3 , and Sm 0.5 Sr 0.5 MnO 3 were grown to provide a series of samples with fixed ratio Mn(III)/Mn(IV)=1 having geometric tolerance factors that span the transition from localized to itinerant electronic behavior of the MnO 3 array. A unique ferromagnetic phase appears at the critical tolerance factor t c = 0.975 that separates charge ordering and localized-electron behavior for tt c . This ferromagnetic phase, which has to be distinguished from the ferromagnetic metallic phase stabilized at tolerance factors t>t c , separates two distinguishable Type-CE antiferromagnetic phases that are metamagnetic. Measurements of the transport properties under hydrostatic pressure were carried out on a compositions t a little below t c in order to compare the effects of chemical vs. hydrostatic pressure on the phases that compete with one another near t=t c .

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“…A recent crystal determination of Pr 0.6 Ca 0.4 MnO 3 manganite [4] has revealed the presence of Zener polarons i.e. trappings of holes (or electrons) within pairs of Manganese sites.…”

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confidence: 99%

“…trappings of holes (or electrons) within pairs of Manganese sites. The Zener polaron was initially assumed to be ruled by a double exchange model [4,5] [6,7] show an important O to Mn charge transfer, resulting in a localization of the holes on the bridging oxygens. This charge distribution suggests a dominant purely magnetic local order (Mn 3+ O − Mn 3+ ) in which the Zener polarons would be ferrimagnetic entities involving an antiferromagnetic coupling between the magnetic oxygen and the high spin manganese centers.…”

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confidence: 99%

Relation between double exchange and Heisenberg model spectra: Application to the half-doped manganites

2007

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The Zener polarons recently found in half-doped manganites are usually seen as mixed valence entities ruled by a double exchange Hamiltonian involving only correlated electrons of the metals. They can however be considered as ferrimagnetic local units if the holes are localized on the bridging oxygen atoms as implicitely suggested by recent mean-field ab initio calculations. In the latter case, the physics is ruled by a Heisenberg Hamiltonian involving magnetic oxygen bridges. This paper shows that the spectra resulting from the resolution of both models are analytically identical. This single resulting model spectrum accurately reproduces the spectrum of Zener polarons in Pr0.6Ca0.4MnO3 manganite studied by means of explicitely correlated ab initio calculations. Since the physics supported by each model are different, the analysis of the exact Hamiltonian ground state wave function should a priori enables one to determine the most appropriate model. It will be shown that neither the spectrum nor the wavefunction analysis bring any decisive arguments to settle the question. Such undecidability would probably be encountered in experimental information. [6,7] show an important O to Mn charge transfer, resulting in a localization of the holes on the bridging oxygens. This charge distribution suggests a dominant purely magnetic local order (Mn 3+ O − Mn 3+ ) in which the Zener polarons would be ferrimagnetic entities involving an antiferromagnetic coupling between the magnetic oxygen and the high spin manganese centers. In the latter case the model Hamiltonian which provides a relevant description of the local electronic order is a Heisenberg Hamiltonian. The holes localization has been a matter of debate in the literature and concerns a large number of materials like doped cuprates [8](where there is at most one unpaired electron per metal resulting in a t-J model), nickelates or manganites (in which there are several open-shells per center leading to a double exchange interaction). Besides, as far as the correlated electrons are only localized on the metallic centers, the comparison of the models has been the subject of intense discussion and controversy which ended up with the demonstration that the two models were strictly different and lead to different spectra [9]. The aim of this paper is to show that when considering a magnetic oxygen in the Heisenberg model the analytical resolution of the two Hamiltonians leads to identical spectra. For this purpose we have derived an analytical solution of the Heisenberg Hamiltonian energies for three magnetic centers.Since the discrimination between the two models is impossible from the spectrum determination, we will then adress this question from wavefunction analysis. Indeed, the projection of the ab initio ground state wavefunction onto both model spaces should a priori determine the choice. However, it will be shown that when the charge of the oxygen is around -1.5, the wavefunction analysis does not infer any decidable argument. In order to illustrate this asserti...

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Zener Polaron Ordering in Half-Doped Manganites

Cited by 287 publications

References 23 publications

Competing crystal structures inLa0.5Ca0.5MnO3: Conventional charge order versus Zener polarons

Competing crystal structures inLa0.5Ca0.5MnO3: Conventional charge order versus Zener polarons

Phase competition inL0.5A0.5MnO3perovskites

Relation between double exchange and Heisenberg model spectra: Application to the half-doped manganites

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