Phase Coexistence and Resistivity near the Ferromagnetic Transition of Manganites

Alexandrov, A. S.; Bratkovsky, A. M.; Kabanov, V. V.

doi:10.1103/physrevlett.96.117003

Cited by 80 publications

(69 citation statements)

References 35 publications

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“…The equation for the insulating branch of R(T ) is therefore R I (T ) = AT exp(− 2k B T ), where A is a constant and is the bipolaron binding energy. We find ß 0.1 eV, consistent with the known values for manganites [24,33] and confirming, when compared with LSMO samples having different grain sizes distributions [72], the general high degree of structural order of the samples.…”

Section: One Comes To the Final Expression For The Metallic Branch R supporting

confidence: 89%

“…3), indicating standard adiabatic hopping in agreement with both experimental data [28] and polaron theory [20]. In particular, this is consistent with the bipolaron theory developed for CMR and enables us to use the CCDC picture to describe the MIT [31,33,71]. The equation for the insulating branch of R(T ) is therefore R I (T ) = AT exp(− 2k B T ), where A is a constant and is the bipolaron binding energy.…”

Section: One Comes To the Final Expression For The Metallic Branch R supporting

confidence: 79%

“…(1 − erf ( T −T t ))} ς represents the fraction of metallic phase; note that a nonideality exponent ς is added in respect to the original CCDC model [31,33]. This way, to mix R M and R I takes count of a phase separation scenario [73], which is known to happen during the MIT in LSMO [74].…”

Section: One Comes To the Final Expression For The Metallic Branch R mentioning

confidence: 99%

“…Concerning the case of a metal-metal transition, we first have to stress that a theory that consistently explains such a transition does not exist, and all the theories for manganites predict a transition towards an insulating state [10,31,33,69,75,76]. Nevertheless, the data above the transition, corresponding to a supposed paramagnetic metallic phase, [70] are described with the electron-phonon coupling term but considering a constant effective mass (since the polaron band picture with the exponential increase of the effective mass is broken) and the temperature acting only on the phonon population n ω .…”

Section: One Comes To the Final Expression For The Metallic Branch R mentioning

confidence: 99%

“…When applied [24][25][26][27][28], this approach gave unrealistic values for the T 5 coefficient, which is found to be one to two orders of magnitude lower than in metals [29,30]. These findings are in obvious contradiction with the strong electronphonon coupling, known to govern the physics of manganites [6,12,18,[31][32][33][34][35]. The basic problem is nevertheless the clear failure of this approach to fit the main R(T ) features when applied in an extended temperature range, as represented in Fig.…”

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confidence: 97%

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Polaron framework to account for transport properties in metallic epitaxial manganite films

et al. 2014

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We propose a model for the consistent interpretation of the transport behavior of manganese perovskites in both the metallic and insulating regimes. The concept of polarons as charge carriers in the metallic ferromagnetic phase of manganites also solves the conflict between transport models, which usually neglects polaron effects in the metallic phase, and, on the other hand, optical conductivity, angle-resolved spectroscopy, and neutron scattering measurements, which identify polarons in the metallic phase of manganites down to 6 K. Transport characterizations of epitaxial La 0.7 Sr 0.3 MnO 3 thin films in the thickness range of 5-40 nm and temperature interval of 25-410 K have been accurately collected. We show that taking into account polaron effects allows us to achieve an excellent fit of the transport curves in the whole temperature range. The current carriers density collapse picture accurately accounts for the properties variation across the metal-insulator transitions. The electron-phonon coupling parameter γ estimations are in a good agreement with theoretical predictions. The results promote a clear and straightforward quantitative description of the manganite films involved in charge transport device applications and promises to describe other oxide systems involving a metal-insulator transition. Ferromagnetic manganites are a prototypical example of the so-called half-metallic materials, i.e., materials with 100% spin polarization at 0 K. Although their possible application in commercial spintronics is prevented by a relatively low Curie temperature (T C 370 K), manganites represent an ideal laboratory tool to test spin transport in various materials and to search for pioneering device paradigms [1,2]. Thus, the use of manganites have significantly contributed to the field of organic spintronics, where almost half of the reported devices have La 0.7 Sr 0.3 MnO 3 (LSMO) as an injector [3]. In this context, revealing in a most exhaustive and comprehensive way, the transport properties of these materials looks both captivating and thought provoking.The transport properties of manganites are strongly linked to their ferromagnetism and are generally described in the framework of the so-called double-exchange mechanism: below T C the exchange interaction between Mn cations through oxygen anions favors ferromagnetism and electron delocalization along the Mn-O-Mn bonds, while above T C , thermal disorder disrupts this delocalization leading to a metal-insulator transition (MIT) [4]. Nevertheless, this basic picture appears to be conceptually insufficient to describe the physics of manganites, in general, and LSMO, in particular [5]: the strong role of polaron effects in manganites has been pointed out [6], and good experimental evidence has been provided by a variety of methods [6][7][8][9][10][11][12][13]. Moreover, manganites were proposed as an example of a polaron Fermi liquid [7].Although the presence of polarons in the metallic phase of LSMO (down to 6 K) has been demonstrated by optical * patrizio.gr...

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Section: One Comes To the Final Expression For The Metallic Branch R supporting

confidence: 89%

Section: One Comes To the Final Expression For The Metallic Branch R supporting

confidence: 79%

Section: One Comes To the Final Expression For The Metallic Branch R mentioning

confidence: 99%

Section: One Comes To the Final Expression For The Metallic Branch R mentioning

confidence: 99%

mentioning

confidence: 97%

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Polaron framework to account for transport properties in metallic epitaxial manganite films

et al. 2014

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Sequential Electronic and Structural Transitions in VO₂ Observed Using X‐ray Absorption Spectromicroscopy

et al. 2014

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Effects of correlated disorder on the magneto‐transport in colossal magnetoresistance manganites

Egilmez

Salman

Chow

et al. 2009

Physica Rapid Research Ltrs

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A number of theories [1][2][3] have been developed to explain the many unusual properties of Mn oxides (manganites). According to the "double-exchange" (DE) model, the MIT and the CMR are a consequence of the doubleexchange mechanism combined with the Jahn-Teller electron-phonon interaction with d-states, leading to the conclusion that the low and high temperature phases are a spin polarized ferromagnetic metal and a polaronic paramagnetic insulator, respectively [1]. More recently the current carrier density collapse theory, on the other hand, postulates that the MIT and the CMR are caused by a magnetic break-up at T c of heavy bipolarons (which are formed by pairing of oxygen p-holes in the paramagnetic phase) [2]. Monte-Carlo (MC) simulations [3,4] suggest that the ground states of manganites tend to be intrinsically inhomogeneous due to strong tendencies toward phase separation in the presence of quenched disorder. The quenched disorder can come from many sources, including the lattice-distorting chemical doping, random fluctuations of dopant density, or strain fields. For example, chemical doping can introduce distortions in the MnO 6 octahedra which cause local disorder that propagates through the lattice because of elastic forces. This propagation of distortions is possible because adjacent MnO 6 octahedra share an oxygen, implying the distortions are cooperative in nature, and hence the quenched disorder is correlated. In this model, the effects of the phase competition between ferromagnetic metallic (FM) and antiferromagnetic insulating Monte-Carlo simulations predict that a local correlated disorder is responsible for many of the novel transport and magnetic properties of colossal magnetoresistance (CMR) materials such as manganites. One important prediction of these models is that the resistivity at the metal -insulator transition (MIT) in manganites depends strongly on the correlated quenched disorder. However, experimental confirmation has been challenging since it is difficult to control the amount of disorder in these compounds. We carried out experiments on Sm 0.55 Sr 0.45 MnO 3 , a prototypical CMR manganite with a sharp MIT, whereby the oxygen-related disorder is systematically enhanced by low temperature thermal activation. We observe dramatic changes in the temperature dependence of resistivity at the MIT as the amount of quenched disorder is increased, occurring in a manner that is in agreement with theoretical predictions.Temperature dependence of resistivity of Sm 0.55 Sr 0.45 MnO 3 for different annealing times at 350 °C in vacuum.

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Phase Coexistence and Resistivity near the Ferromagnetic Transition of Manganites

Cited by 80 publications

References 35 publications

Polaron framework to account for transport properties in metallic epitaxial manganite films

Polaron framework to account for transport properties in metallic epitaxial manganite films

Sequential Electronic and Structural Transitions in VO₂ Observed Using X‐ray Absorption Spectromicroscopy

Effects of correlated disorder on the magneto‐transport in colossal magnetoresistance manganites

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Phase Coexistence and Resistivity near the Ferromagnetic Transition of Manganites

Cited by 80 publications

References 35 publications

Polaron framework to account for transport properties in metallic epitaxial manganite films

Polaron framework to account for transport properties in metallic epitaxial manganite films

Sequential Electronic and Structural Transitions in VO2 Observed Using X‐ray Absorption Spectromicroscopy

Effects of correlated disorder on the magneto‐transport in colossal magnetoresistance manganites

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Sequential Electronic and Structural Transitions in VO₂ Observed Using X‐ray Absorption Spectromicroscopy