Characteristics of the phase-separated state in manganites: Relationship with transport and magnetic properties

Кugel, K. I.; Rakhmanov, A. L.; Sboychakov, A. O.; Kagan, M. Yu.; Brodsky, I. V.; Klaptsov, A. V.

doi:10.1134/1.1705710

Cited by 27 publications

(25 citation statements)

References 14 publications

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“…For the characteristic values of parameters, a droplet includes 10-30 unit cells. These results could, in particular, serve as a key to an adequate description of the transport properties of manganites that could not be done in the framework of the single-band models 20,21 . As it was mentioned above, various models related to the strongly correlated electrons exhibit a pronounced tendency toward phase separation.…”

Section: Discussionmentioning

confidence: 99%

“…The theoretical models usually imply that the number of charge carriers introduced by doping is equal to the number of itinerant electrons which take part in the formation of nanoscale inhomogeneities. However, the comparison of experimental data with the theoretical results suggests that such an approach is insufficient 19 and the number of self-trapped carriers can significantly differ from the doping level 20,21 . Here, we analyze the model proposed in our paper Ref.…”

Section: Introductionmentioning

confidence: 99%

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Jahn-Teller distortions and phase separation in doped manganites

2006

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A "minimal model" of the Kondo-lattice type is used to describe a competition between the localization and metallicity in doped manganites and related magnetic oxides with Jahn-Teller ions. It is shown that the number of itinerant charge carriers can be significantly lower than that implied by the doping level x. A strong tendency to the phase separation is demonstrated for a wide range of intermediate doping concentrations vanishing at low and high doping. The phase diagram of the model in the x − T plane is constructed. At low temperatures, the system is in a state with a long-range magnetic order: antiferromagnetic (AF), ferromagnetic (FM), or AF-FM phase separated (PS) state. At high temperatures, there can exist two types of the paramagnetic (PM) state with zero and nonzero density of the itinerant electrons. In the intermediate temperature range, the phase diagram includes different kinds of the PS states: AF-FM, FM-PM, and PM with different content of itinerant electrons. The applied magnetic field changes the phase diagram favoring the FM ordering. It is shown that the variation of temperature or magnetic field can induce the metal-insulator transition in a certain range of doping levels.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Jahn-Teller distortions and phase separation in doped manganites

2006

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“…However, we should take into account that wave functions ψ (n) g are not independent because of the orthogonality conditions (6). Calculating the derivatives ∂F appr /∂ψ…”

Section: A Approximate Partition Functionmentioning

confidence: 99%

“…Indeed, there are a lot of experimental indications (coming mostly from the susceptibility and ESR data) that manganites in the paramagnetic state are rather inhomogeneous. Moreover, the analysis of the hightemperature transport properties of manganites based on the assumption of the existence of ferromagnetically correlated regions in the paramagnetic phase gives a viable picture of the inhomogeneous state [6].…”

Section: Introductionmentioning

confidence: 99%

Evolution with temperature of the magnetic polaron state in an antiferromagnetic chain with impurities

et al. 2005

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The thermal behavior of a one-dimensional antiferromagnetic chain doped by donor impurities was analyzed. The ground state of such a chain corresponds to the formation of a set of ferromagnetically correlated regions localized near impurities (bound magnetic polarons). At finite temperatures, the magnetic structure of the chain was calculated simultaneously with the wave function of a conduction electron bound by an impurity. The calculations were performed using an approximate variational method and a Monte Carlo simulation. Both these methods give similar results. The analysis of the temperature dependence of correlation functions for neighboring local spins demonstrated that the ferromagnetic correlations inside a magnetic polaron remain significant even above the Néel temperature T N implying rather high stability of the magnetic polaron state. In the case when the electron-impurity coupling energy V is not too high (for V lower that the electron hopping integral t), the magnetic polaron could be depinned from impurity retaining its magnetic structure. Such a depinning occurs at temperatures of the order of T N . At even higher temperatures (T ∼ t) magnetic polarons disappear and the chain becomes completely disordered.

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“…It is often taken for granted that all charge carriers generated by the doping take part in the formation of FM droplets. At the same time, the analysis of experimental data (in particular, of spin-dependent magnetotransport) demonstrates that the doping level and the number of self-trapped carriers can differ drastically [3]. Here, we discuss a model relating the doping level and the number of the charge carriers.…”

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confidence: 96%