Polaron liquid-gas crossover at the orthorhombic-rhombohedral transition of manganites

Souza, J. A.; Terashita, H.; Granado, E.; Jardim, R. F.; Oliveira, N. F.; Muccillo, R.

doi:10.1103/physrevb.78.054411

Cited by 18 publications

(19 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For the simulation an electric quadrupolar coupling ν Q = e 2 qQ h = 21MHz, asymmetry parameter n = 0.5 and a dipole-dipole interaction of the La nuclear sites with the Mn ions of ≈ 20kHz were considered. By decreasing temperature, at T ≈ 700K, a significant increase of the SFD width is observed, which marks the transition from the R − 3c to the P nma crystal structure 28 , and the appearence of strong incoherent JT displacements. This structural phase transformation is shown by synchrotron radiation measurements to be independent of the applied magnetic field 28 .…”

Section: High Temperaturementioning

confidence: 97%

Spin order and lattice frustration in optimally doped manganites: A high-temperature NMR study

et al. 2010

View full text Add to dashboard Cite

The physics underlying the complex glassy phenomena, which accompany the formation of polarons in optimally doped manganites (ODM) is a cumbersome issue with many unexplained aspects. In this article we present 139 La and 55 Mn NMR in the temperature range 80K -900K of ODM La0.67Ca0.33MnO3. We show that local lattice distortions, established in the Paramagnetic (PM) phase for T < 700K, induce a genuine spin-glass state, which for T < Tc consolidates with the Ferromagnetic (FM) state into a single thermodynamic phase. Comparative NMR experiments on La0.77Ca0.23MnO3, La0.59Ca0.41MnO3, and La0.70Sr0.30MnO3 demonstrate the dominant role of lattice distortions, which appear to control (i) the stability of the spin glass phase component and (ii) the kind (1st or 2nd order) of the PM-FM phase transition. The experimental results are in agreement with the predictions of the compressible random bond -random field Ising model, where consideration of a strain field induced by lattice distortions, is shown to invoke at Tc a discontinuous (1st order like) change of both the FM and the "glassy" Edwards-Anderson (EA) order parameters.

show abstract

Section: High Temperaturementioning

confidence: 97%

Spin order and lattice frustration in optimally doped manganites: A high-temperature NMR study

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The spatial (domain size) and temporal scales of these domains are probably too small to be observed by diffraction techniques. Several papers in the literature relate the presence of an hysteresis to the existence of phase mixing in similar compounds 23,[33][34][35] . The occurrence of mixed phases in LaM nO 3 under pressure has already been pointed out by Baldini and coworkers 18 in a similar pressure range.…”

mentioning

confidence: 99%

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

Ramos

Souza-Neto

Tolentino

et al. 2011

EPL

View full text Add to dashboard Cite

Using X-ray absorption spectroscopy (XAS), we studied the local structure in LaMnO3 under applied pressure across and well above the insulator to metal (IM) transition. A hysteretic behavior points to the coexistence of two phases within a large pressure range (7 to 25 GPa). The ambient phase with highly Jahn-Teller (JT) distorted M nO6 octahedra is progressively substituted by a new phase with less-distorted JT M nO6 units. The electronic delocalization leading to the IM transition is finger-printed from the pre-edge XAS structure around 30 GPa. We observed that the phase transition takes place without any significant reduction of the JT distortion. This entails band-overlap as the driving mechanism of the IM transition.PACS numbers: 61.50. Ks,71.70.Ej, 71.30.+h LaMnO 3 is the parent compound of a family of doped manganates that exhibit a multitude of electronic phases and unusual properties with strong potential for new electronic devices 1 . The compound crystallizes in the orthorhombically distorted perovskite structure (space group Pbmn), in which every M n 3+ ion with high-spin configuration tis surrounded by an octahedron of six oxygen ligands. Under ambient conditions, the Jahn-Teller (JT ) instability of the singly occupied e g orbitals gives rise to cooperative distortions of the M nO 6 octahedra, which induce orbital ordering and may be responsible for the insulating behavior of LaMnO 3 . Although the ground-state of LaMnO 3 can be explained both by cooperative JT distortion and orbital exchange interaction, their relative importance lead to different physics for the doped systems and is then an important issue for predicting and optimizing physical properties. However, the separation of the two effects is a very delicate issue 2-8 that calls for accurate experimental probes.At ambient pressure LaMnO 3 undergoes at T IM =710 K an insulator to metal (IM) transition, structurally described as a transition from an ordered toward a disordered array of JT distorted octahedra. The long range structure is characterized by a strong cell symmetrization and the loss of the orbital order 9 . The local scale JT splitting persists essentially unaltered across the IM transition, which is marked by the symmetrization of the thermal fluctuations in the distorted M nO 6 units 10,11 .At ambient temperature, transition towards a metal state can also be attained by application of external hydrostatic pressure. High pressure reduces lattice parameters, favoring orbital overlap and concomitant enhancement of electron delocalization. It also forces an atomic rearrangement, tending to reduce lattice distortions (inter-octahedral and intra-octahedra rearrangements). In LaMnO 3 the IM transition has been reported by Loa and coworkers at an applied pressure of 32 GPa 12 . Using X-ray diffraction under pressure, these authors obtained refined atomic positions up to 11 GPa 12 . From an extrapolation of their results, they predict that the local JT distortion should completely vanish around 18 GPa. However, in a previous X-ray ...

show abstract

“…By decreasing temperature, at T ≈ 710 K, an abrupt increase of the SFD width is observed, which marks the transition from the R3c to the Pnma crystal structure and the onset of strong incoherent JT displacements. 39,40 Neutron scattering experiments indicate that the appearance of the JT distortions is related with the formation of uncorrelated dynamic JT polarons right below T RO , which by further decreasing temperature freeze into a CE-type polaron glassy state with correlation length of ≈1 nm. 9 Most notable, for T < 100 K spectra start to broaden and shift to higher frequency, which might indicate the onset of an until now unnoticed novel FM phase.…”

Section: Vzzmentioning

confidence: 99%

“…It is furthermore noticed that for T < T c the magnetic field B at the site of the La nuclei is equal to the sum of the applied external field B and the transferred hyperfine field B hf ¼ ð1=γ hÞA S h i, where A is the hyperfine coupling constant and S h i the average electronic spin of the eight nearest Mn neighbors. 38,39 Figure 1a demonstrates 139 La NMR spectra of the LCMO(0.33) system in the temperature range 3.2-900 K. LCMO(0.33) undergoes two major phase transitions: a structural one from the high temperature R3c rhombohedral phase to the low temperature orthorombic Pnma phase at T RO ≈ 710 K, 39,40 and a paramagnetic to FM (PM-FM) one at T c = 267 K, as shown in Figures S3.1, S3.2 and S5.1 of the Supplementary Information. The critical temperature of the PM-FM phase transition T c , defined as the inflection point of the frequency vs. T plot, in the magnetic field of 9.4 T is found to be T c ≈ 300 K (right bottom inset), sufficiently higher than in zero external magnetic field.…”

Section: Vzzmentioning

confidence: 99%

“…In case of the LSMO(0.30) system, which remains in the R3c crystallographic phase at all temperatures, 1/w vs. T follows a linear Curie-Weiss law, crossing the horizontal T axis at T c ≈ 400 K. Similarly, LCMO(0.41), which shows only dynamic CE-type polaronic distortions in the PM phase, 9 and no SFD was observed in the relevant 139 La NMR spectra, 1/w follows the Curie-Weiss law down to T c ≈ 300 K. However, in case of LCMO(0.23) and LCMO (0.33), where JT static polarons have been detected with neutron scattering experiments, 9 strong deviation from the linear Curie-Weiss relation is observed in the temperature range 400-550 K, in agreement with magnetic susceptibility measurements. 40 This deviation signalizes the transition from the dynamic to the static polaron regime. 9,39,40 It is also tempting to consider that for T > 550 K electron spin dynamics in both the LCMO (0.23,0.33) systems are dominated by magnetic correlations of the high temperature R3c phase, while for T < 400 K the formation of the static CE-type polaronic distortions dominates their magnetic properties.…”

Section: Vzzmentioning

confidence: 99%

See 1 more Smart Citation

Polaron freezing and the quantum liquid-crystal phase in the ferromagnetic metallic La0.67Ca0.33MnO3

et al. 2018

View full text Add to dashboard Cite

The remarkable electronic properties of colossal magnetoresistive manganites are widely believed to be caused by the competition between a ferromagnetic metallic state and an antiferromagnetic insulating state with complex spin, charge, and orbital ordering. However, the physics underlying their magnetotransport properties is still not clear, especially the role of correlated Jahn-Teller polarons, which depending on temperature and doping, might form a liquid, glass or stripe polaron state. This question touches one of the most fundamental problems in the physics of doped Mott insulators, i.e. understanding the mechanism that chemical doping makes an insulator becoming superconductive as in the case of cuprates, or exhibiting the colossal magnetoresistance effect, as in the case of manganites. Here, by using 139 La NMR and high resolution transmission electron microscopy in the temperature range 3.2-1000 K, we have monitored the formation and evolution of CE-type polarons in optimally doped La 0.67 Ca 0.33 MnO 3 . While NMR experiments show that correlated polarons dominate electron spin dynamics in the ferromagnetic phase, at very low temperatures they appear to form a quantum liquid-crystal like ferromagnetic phase, embedded into a ferromagnetic matrix with 3D polaron correlations. This is evidence that similarly to high T c cuprates, quantum soft phases underlie the exotic physical properties of colossal magnetoresistive manganites.

show abstract

Polaron liquid-gas crossover at the orthorhombic-rhombohedral transition of manganites

Cited by 18 publications

References 50 publications

Spin order and lattice frustration in optimally doped manganites: A high-temperature NMR study

Spin order and lattice frustration in optimally doped manganites: A high-temperature NMR study

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

Polaron freezing and the quantum liquid-crystal phase in the ferromagnetic metallic La0.67Ca0.33MnO3

Contact Info

Product

Resources

About

Polaron liquid-gas crossover at the orthorhombic-rhombohedral transition of manganites

Cited by 18 publications

References 50 publications

Spin order and lattice frustration in optimally doped manganites: A high-temperature NMR study

Spin order and lattice frustration in optimally doped manganites: A high-temperature NMR study

Bandwidth-driven nature of the pressure-induced metal state of LaMnO 3

Polaron freezing and the quantum liquid-crystal phase in the ferromagnetic metallic La0.67Ca0.33MnO3

Contact Info

Product

Resources

About

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃