Antiferromagnet-ferromagnet phase transition in lightly doped manganites

Troyanchuk, I. O.; Khomchenko, V. A.; Eremenko, V. V.; Sirenko, V. A.; Szymczak, H.

doi:10.1063/1.2008144

Cited by 4 publications

(4 citation statements)

References 32 publications

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“…Physical properties of the compounds of stoichiometric cation composition were found to be adjusted by changing the oxygen nonstoichiometry [10]. Self-doped compounds La 0,88 MnO x undergo a sequence of transitions: orbitally ordered antiferromagnetic (x=2.82)ferromagnetic insulator (x=2.9) -ferromagnetic metal (x>2.91) with increasing oxygen content and increasing manganese valence [11]. Due to heterovalent substitution of cations in doped manganites Ln 1-x A x MnO 3±δ (Ln= rare earth element, A = divalent metal cation, δ = oxygen non-stoichiometry), there is a variable oxidation degree of manganese, which is responsible for the appearance of the colossal magnetoresistance and other unique properties of these materials [12].…”

Section: Introductionmentioning

confidence: 99%

Structural Properties of Mechanically Activated Rare-Earth Manganites

Федорова¹,

Фетисов²,

Fishman³

et al. 2014

cme

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The effect of mechanical processing in different types of activators on the structure and physicochemical properties of the oxides LnMnO 3+δ (Ln = Sm, Nd, La) has been studied. The optimal modes of mechanical activation for transformation the oxides under consideration to nanostructured state have been defined. Mechanical processing has been shown to cause a significant change of Jahn-Teller distortion parameters and temperatures of the cooperative Jahn-Teller phase transition. The presence of connection between redox processes and destruction of orbital ordering has been demonstrated. Very low values (10 -21 -10 -24 m 2 /s) of the oxygen bulk diffusion coefficient have been obtained for the oxides under consideration in the temperature range of 400 -750°C. The diffusion activation energies are close to 1 eV, indicating the oxygen diffusion proceeds through structural defects at these temperatures.

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Section: Introductionmentioning

confidence: 99%

Structural Properties of Mechanically Activated Rare-Earth Manganites

Федорова¹,

Фетисов²,

Fishman³

et al. 2014

cme

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“…Some interesting properties exhibited by these materials include ferromagnetism, 2,3 colossal magnetoresistance, 4,5 half metallicity, 6 orbital ordering, 7,8 the dynamic Jahn–Teller effect, 9 and the polaronic effect 10 . These properties arise from a variety of possible phase states, transitions, and intrinsic correlations of the crystal structure, magnetic characteristics, and transport properties.…”

Section: Introductionmentioning

confidence: 99%

“…The lanthanum manganites have a large number of technological applications, such as in transducers and nonvolatile memory devices and as cathode materials in solid oxide fuel cells 11 . Despite their widespread applications and the numerous studies devoted to these materials, 12 the nature of the interplay between the crystal structure, magnetic properties, and transport properties of manganites is still not entirely understood.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure Analysis of Calcium‐Doped Lanthanum Manganites Prepared by Mechanosynthesis

Lira-Hernández

Jesús

Cortés-Escobedo³

et al. 2010

Journal of the American Ceramic Society

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We report results of crystal structure analyses of calcium‐doped lanthanum manganites, La1−xCaxMnO3, obtained by mechanosynthesis. The calcium to lanthanum ratio x was varied from 0 to 1 at increments of 0.1, allowing us to study changes in crystal structure with different degrees of calcium substitution, from LaMnO3 (x=0) to CaMnO3 (x=1). Metallic oxide precursors, Mn2O3, La2O3, and CaO, were mixed in stoichiometric proportions. The powder mixture was milled using a shaker mixer/mill. X‐ray powder diffraction was used to monitor the phase transformation as a function of the milling time. Rietveld refinement was used to structurally characterize the manganites. The results show that it is possible to obtain calcium‐doped lanthanum manganite by mechanosynthesis using a weight ratio of balls to powder of 12:1. After 4.5 h of milling time, the synthesis is completed; the time is independent of the calcium‐doping level. However, increase of the Ca2+ content leads to a monotonic decrease of the orthorhombicity factor b/a for calcium to lanthanum ratios between 0.2 and 0.8. When the doped level is increased, a peak displacement is observed, which is associated with a distortion of the crystal structure and variation in the cell parameter. All the manganites crystallized with the same O‐type orthorhombic perovskite structure as pure LaMnO3, with a space group Pnma. The structural distortion in the orthorhombic lattice with the Ca2+ content is associated with a partial oxidation of the manganese ion, the increment on vacancies, and the cationic substitution.

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“…29 and 30)-has an extremely high sensitivity to the variations in oxygen content. 31,32 Its study helps to clarify the general tendencies of the formation of the low-temperature magnetic state in manganites, which is responsible for CMR. Extensive studies of the magnetic properties of manganites by all known methods have demonstrated that the magnetic ordering, which occurs upon cooling, is usually accompanied by the formation of an instability region.…”

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Irreversibility and anisotropy of the low-temperature magnetization in manganites. Spin-glass polyamorphism

Sirenko

Eremenko

2014

Low Temperature Physics

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The temperature dependences of the magnetization in manganites of different composition and structural morphology were measured in two cooling regimes, field cooling (FC) and zero-field cooling (ZFC), for two different orientations of a magnetic field, parallel and perpendicular to the c-axis. The following general tendencies were found: (1) The difference between the magnetizations M FC and M ZFC at T ¼ 5 K increases with increasing magnetic field, reaching the maximum value in a magnetic field of about 2 kOe, and then drops in the range 2-5 kOe; (2) The field dependence of the "splitting" temperature T * below which the difference between the magnetizations M FC and M ZFC appears can be reasonably well described by a power law with the exponent 2/3 as predicted by the theory of spin glasses. Both results are characteristic for single crystals, as well as for ceramics and films. On the other hand, the field dependence of the anisotropy of magnetic susceptibility is different for samples with different degrees of magnetic ordering (H/T C ). These results are consistent with the detected in the present study universality of the line separating the low-temperature region of irreversibility in the H-T phase diagram of manganites. Deviations from the T * -H-line with the exponent 2/3 in strong magnetic fields, which are commonly associated with the appearance of the magnetization component transverse to the magnetic field, are typical for samples containing the antiferromagnetic phase. The interpretation takes into account the multi-phase nature of the systems, i.e., coexistence of spin glass with ferromagnetism and antiferromagnetism. The observed change in the anisotropy of magnetic susceptibility with increasing magnetic field and the behavior of magnetic and thermomagnetic irreversibility are regarded as a manifestation of the spin-reorientation phase transition in an antiferromagnetic environment. This in turn initiates the transformation of the spin-glass-from the Ising-to the Heisenberg-type-which leads to the change in the exponent in the T * -H diagram from 2/3 to 2. The observed phenomenon is universal-it was observed in manganites of different composition and structural morphology-and represents a particular type of polyamorphism, namely, spin-glass polyamorphism. V C 2014 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4865567] Low Temp. Phys. 40 (2), February

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Antiferromagnet-ferromagnet phase transition in lightly doped manganites

Cited by 4 publications

References 32 publications

Structural Properties of Mechanically Activated Rare-Earth Manganites

Structural Properties of Mechanically Activated Rare-Earth Manganites

Crystal Structure Analysis of Calcium‐Doped Lanthanum Manganites Prepared by Mechanosynthesis

Irreversibility and anisotropy of the low-temperature magnetization in manganites. Spin-glass polyamorphism

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